Second Workshop on
Experimeental Laaboratoryy Astropphysics
Poipu, Kauai,
K
Haw
waii, Februaary 23-26, 2015
The second workshop will take place at the Sheraton Kauai Resort in Poipu, Kauai, Hawaii, starting with
a reception and registration on February 22, 2015, at 6 pm. Based on the success and enthusiasm of the
first workshop in 2013, the workshop again features invited (senior and junior researchers) as well as
contributed talks and poster presentations focusing on the interaction of ionizing radiation (UV, VUV,
gamma rays, charged particles) and neutrals (atoms, radicals, molecules, grains) with low temperature
solids (ices, minerals, organics). Presentations have been extended to include observations, modeling, and
electronic structure calculations that can directly link to laboratory experiments.
During the last decade, significant new experimental techniques have been developed to
investigate the interaction of ionizing radiation (UV, VUV, gamma rays, charged particles) and
of neutrals (atoms, radicals, molecules, grains) with surfaces of solids (ices, minerals,
carbonaceous compounds) in the Solar System and in the Interstellar Medium (ISM). These
processes provide new fundamental insights into the processes that are critical to the chemistry in the
ISM, star and planet forming regions, and on/in icy objects in the Solar System ranging from the
formation of the simplest molecule (molecular hydrogen) to astrobiologically important species such as
amino acids and sugars. Considering the highly anticipated results from space craft missions such as New
Horizons and Rossetta, there is an increasing necessity for the dissemination of laboratory results. As
such we are grateful that so many of you have utilized this opportunity to present your work to the
community and hope that this level of enthusiasm will continue to provide a solid foundation for future
workshops to come.
We are looking forward to seeing you on Kauai in 2015.
Sincerely,
The Organizers
Brant Jones, University of Hawaii at Manoa
Murthy Gudipati, JPL
Mark Loeffler, NASA Goddard
Gianfranco Vidali, Syracuse University
Helen Fraser, Open University, UK
Ralf I. Kaiser, University of Hawaii at Manoa
Naoki Watanabe, University of Hokkaido, Japan
Time
Monday
Tuesday
Wednesday
Thursday
Session Chair
Brant Jones
Gianfranco Vidali
Karin Öberg
Ralf Kaiser
8:00 – 8:40
Louis le Sergeant
d’Hendecourt
(8:20 – 9:00)
Murthy Gudipati
Gianfranco Vidali
Helen Fraser
8:40 – 9:20
Pierre de Marcellus
(9:00 – 9:20)
Lucy Ziurys
Jean Louis Lemaire
9:20 – 10:00
Laurent Nahon
Pascale
Ehrenfreund
David Anderson
10:00 – 10:20
Guillermo
Manuel Muñoz
Caro
Jean-Hugues
Fillion
Break with snacks
Session Chair
Murthy Gudipati
Steven Sibener
Reggie Hudson
Patrice Theulé
10:20 – 11:00
Adwin Boogert
Reggie Hudson
Yu-Jung Chen
Lahouari Krim
11:00 – 11:25
Ralf Kaiser
Lisseth Gavilan
Brett McGuire
Marko Förstel
11:25 – 12:05
Sergio Ioppolo
Naoki Watanabe
Thomas Henning
Katherine Tran
12:05 – 12:25
Paul Brumer
Yuki Kimura
Andrew Turner
Brant Jones
12:25 – 1:05
Steven Sibener
Karin Öberg
Jean-Baptiste Bossa
Albert Rimola
1:05 – 6:00
Free Time
Session Chair
Naoki Watanabe
Dag Hanstorp
Thomas Orlando
6:00 – 6:40
Bing-Ming Cheng
Thomas Orlando
Emmanuel Dartois
6:40 – 7:05
Matthew Abplanalp
Marie-Aline
Martin-Drumel
Sven Thorwirth
7:05 – 7:45
Musahid Ahmed
Yuan-Pern Lee
Liv Hornekær
7:45 – 8:05
Niels Ligterink
Martina D’Angelo
Daniel
Paardekooper
8:05 – 8:25
Break with snacks
Session Chair
Wolf Geppert
Sergio Ioppolo
8:25 – 9:05
Léon Sanche
Dag Hanstorp
Robert Continetti
Thushara Perera
Patrice Theulé
Wolf Geppert
9:05 – 9:25
9:25 – 10:05
Poster Session
End of
Conference
WHY INTERSTELLAR ICES CAN BE CONSIDERED AS PRECURSORS FOR
PREBIOTIC CHEMISTTRY?
Louis le Sergeant d’hendecourt,ab
a
Univ. Paris-Sud, Institut d’Astrophysique Spatiale, « Astrochimie et Origines », UMR 8617, F91405 Orsay, France; eCNRS, France
[email protected]
ABSTRACT
Interstellar ices made of quite simple and basic molecules (H2O, CO, CO2, CH3OH, NH3, CH4,
etc.) are, by far, the most abundant molecular species in the universe (if one excepts H2),
observed in molecular clouds where protostellar objects are detected. Since the constitutive
elements (H, O, C, N, S (and P?)) are the most cosmically abundant, available and condensable,
they are prone to favour the making of ices on solid grains. In the bulk mantles formed around
silicates (or carbon) cores, a rich organic chemistry can develop and, thanks to the protective
nature of the grains against destruction processes and because of their extremely high density
(that of a solid namely), this organic chemistry leads to a very high chemical organic complexity.
Radical chemistry generated by photo/thermos-chemical processes on these surfaces, may well
leave to the formation of solid organic residues similar to those that routinely produced in the
laboratory with ice templates and studied much further, using methods that are unusual in the
astrophysical/chemical community but pertain to cosmochemistry (meteorites) and analytical
chemistry. The organic material formed in these processes may resemble the Soluble Organic
Matter observed in pristine meteorite. From numerous amino acids [1] aldehydes and sugars [2]
detected in these residues to chiral molecules and enantiomeric excesses produced by ultraviolet
Circularly Polarized Light from synchrotron radiation [3], one might seriously ask whether the
chemistry of molecular clouds out of which stars, planetary systems and debris (comets,
asteroids, dust) form, may not be seriously considered as the precursor of prebiotic chemistry
that will take place in a given environment at the surface of a telluric planet as it may have been
the case for the Earth.
I will present the general frame of these experiments in relation with the possibly feeding of the
necessary prebiotic chemistry at the origin of life. Certainly, prebiotic chemistry is very different
in itself than astrochemistry but the starting bricks issued from astrochemistry may well be
necessary for the possibility of developing life on planets under certain assumptions I will briefly
discuss.
REFERENCES
[1] Meinert, C., Filippi, J.-J., de Marcellus, P., Le Sergeant d’Hendecourt, L. and Meierhenrich,
U.J., ChemPlusChem, 77, 186-191 (2012).
[2] de Marcellus, P., Meinert, C., Myrgorodska, I., Nahon, L., Buhse, T., Le Sergeant
d’Hendecourt, L., Meierhenrich, U.J., PNAS, January 12th, 2015
[3] Modica, P., Meinert, C. de Marcellus, Nahon, L., Meierhenrich, U.J., Le Sergeant
d’Hendecourt, L. Astrophys.J, 788, 79
THE IMPORTANCE OF PRE-COMETARY ICES IN ASTROCHEMICAL AND
PREBIOTIC EVOLUTION
Pierre de Marcellusa, Cornelia Meinertb,e, Iuliia Myrgorodskab,c, Laurent Nahonc, Thomas
Buhsed, Louis Le Sergeant d’Hendecourta,e, and Uwe J. Meierhenrichb
a
Univ. Paris-Sud, Institut d’Astrophysique Spatiale, UMR 8617, F-91405 Orsay, France; bUniv.
Nice Sophia Antipolis, Institut de Chimie de Nice, UMR 7272 CNRS, F-06108 Nice, France;
c
Synchrotron SOLEIL, F-91192 Gif-sur-Yvette, France; dCentro de Investigaciones Químicas,
Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, 62209 Cuernavaca,
Mexico; eCNRS, France
[email protected]
ABSTRACT
Interstellar ices (H2O, CO, CO2, CH3OH, NH3, CH4, etc.) are widely observed in the midinfrared range around protostellar objects [1], from which planets, comets and asteroids may
ultimately form. In the laboratory, experiments simulating the energetic (UV photons, cosmic
rays) and thermal evolution of ice analogues lead, after warming the sample up to room
temperature, to the formation of a water-soluble semi-refractory organic residue. Theses residues
have been studied thanks to numerous analytical techniques over the last thirty years, allowing
their partial physical and chemical characterisation [2] and showing that they contain a wide
variety of organic molecules, some of them of potential prebiotic interest, such as amino and diamino acids [3]. They can then be considered as analogues of pre-cometary and/or meteoritic
organic matter, in particular the soluble part (SOM).
I will present our last analyses in which we have detected aldehydes and sugars for the first time
in such laboratory residues [4]. I will discuss the potential implication of these results for
prebiotic chemistry, within an astrophysical scenario that emphasizes the central role of
extraterrestrial ice photo/thermo-chemistry as an ubiquitous phenomenon in protostellar media
and protoplanetary disks environments.
REFERENCES
[1] Öberg, K.I., Boogert, A.C.A., Pontoppidan, K.M. et al., The Astrophysical Journal, 740, 109124 (2011).
[2] Danger, G., Orthous-Daunay, F.-R., de Marcellus, P. et al., Geochimica et Cosmochimica
Acta, 118, 184–201 (2013).
[3] Meinert, C., Filippi, J.-J., de Marcellus, P., Le Sergeant d’Hendecourt, L. and Meierhenrich,
U.J., ChemPlusChem, 77, 186-191 (2012).
[4] de Marcellus, P., Meinert, C., Myrgorodska, I., Nahon, L., Buhse, T., Le Sergeant
d’Hendecourt, L., Meierhenrich, U.J., PNAS, submitted.
ASTROPHYSICAL SCENARI FOR THE ORIGIN OF BIOMOLECULAR ASYMMETRY
PROBED BY CIRCULARLY-POLARIZED VUV SYNCHROTRON RADIATION
Laurent Nahon
Synchrotron SOLEIL
[email protected]
Synchrotron radiation appears to be a very valuable tool for laboratory astrophysics able to
simulate the VUV spectrum of light (including Lyman-α) encountered in the ISM and planetary
ionospheres. This is especially the case of the DESIRS beamline [1] at SOLEIL providing an
intense, tunable, high resolution, VUV radiation with controlled polarizations, including
Circularly Polarized Light (CPL).
This last characteristics allows the study of several asymmetric photon-induced processes which
could be part of an abiotic astrophysical scenario linked to the origin of life’s homochirality, the
fact for instance that only L-amino acids are found in the biosphere. Assuming an extraterrestrial formation of building blocks of life such as amino-acids, a possible abiotic explanation
for the selection of the L enantiomers could be the exposure to CPL as an asymmetric bias
during their journey towards Earth, inducing some enantiomeric excess (e.e) than could then be
amplified on Earth.
After an introduction to the laboratory astrophysics opportunities opened by VUV synchrotron
radiation, asymmetric photon-induced processes leading to noticeable ee will be described:
(i) The photon wavelength-controlled enantio-selective photolysis of racemic solid-films on the
alanine amino acid leading to e.e. of up to 4 %,[2] as measured by 2D-GCMS techniques, in
direct connection with anisotropy spectra recorded on similar samples.[3]
(ii) Photochirogenesis on CPL-irradiated interstellar achiral ice analogs (H2O, NH3, CH3OH)
leading to the asymmetric production of several amino acids with e.e up to 2.5 % for alanine, and
with the same e.e sign for all amino acids at given wavelength. These excesses reverse sign by
swapping the light helicity, showing a chirality transfer from photon to matter.[4]
(iii) Photoelectron Circular Dichroism on gas phase alanine,[5] an asymmetric photoemission
process observed as an intense asymmetry of the ejected electrons and therefore of the
corresponding amino-acid recoiling ion, leading in a given light of sight to an e.e of up to 4 % at
the Lyman α wavelength.[6]
[1]
[2]
[3]
[4]
[5]
[6]
L. Nahon, N. de Oliveira, G. Garcia, J. F. Gil, B. Pilette, O. Marcouille, B. Lagarde, and F.
Polack, J. Synchrotron Rad. 19, 508 (2012).
C. Meinert, S. V. Hoffmann, P. Cassam-Chenaï, A. C. Evans, C. Giri, L. Nahon, and U. J.
Meierhenrich, Angew. Chem.-Int. Edit. 53, 210 (2014).
C. Meinert, J. H. Bredehoeft, J. J. Filippi, Y. Baraud, L. Nahon, F. Wien, N. C. Jones, S. V.
Hoffmann, and U. J. Meierhenrich, Angew. Chem.-Int. Edit. 51, 4484 (2012).
P. Modica, C. Meinert, P. de Marcellus, L. Nahon, U. J. Meierhenrich, and L. L. S. d'Hendecourt,
The Astrophysical Journal 788, 79 (2014).
M. Tia, B. Cunha de Miranda, S. Daly, F. Gaie-Levrel, G. A. Garcia, L. Nahon, and I. Powis, J.
Phys. Chem. A 118, 2765 (2014).
M. Tia, B. Cunha de Miranda, S. Daly, F. Gaie-Levrel, G. Garcia, I. Powis, and L. Nahon, J.
Phys. Chem. Lett. 4, 2698 (2013).
THE COMPOSITION OF INTERSTELLAR ICES
Adwin Boogert
Universities Space Research Association, Stratospheric Observatory for Infrared
Astronomy, NASA Ames Research Center, MS 232-11, Moffett Field, CA 94035, USA
[email protected]
ABSTRACT
Infrared spectroscopy of dense clouds and young stars has led to the secure identification of just
a handful of species embedded in the ice mantles on refractory grains (Boogert, Gerakines, &
Whittet, 2015): H2O, CO, 13CO, CO2, 13CO2, CH3OH, NH3, and CH4. All other proposed ice
species are less securely identified on the basis of a single absorption feature, which for some is
well fitted (peak position and shape) by laboratory spectra (H2CO, OCN-, OCS), but not for
others (e.g., HCOOH, NH4+). Conversely, the origin of a number of interstellar ice absorption
features is highly uncertain. Often, for lack of proper identifications with species produced by
cold grain surface chemistry, these features are considered candidates for production by
energetic processes (UV photons and energetic particles; e.g., Schutte & Khanna 2003, Gibb et
al. 2002). The continued search for carriers relies on the availability of laboratory spectra. Basic
chemistry (Theule et al. 2013), cometary ices (Mumma & Charnley 2011), and gas phase
observations of cloud edges and hot cores (Herbst & van Dishoeck 2009) may be used as a
guidance in the search for new carriers of the interstellar ice features. In the identification
process with laboratory spectra, the widest possible spectral range must be considered (in the
telluric windows and ISO, Spitzer, and future JWST wavelength ranges). Also, appropriate
interstellar targets must be considered because the ice composition is known to vary
considerably.
•
•
•
•
•
•
REFERENCES
Boogert ACA, Gerakines PA, Whittet DCB, Annual Review of Astronomy and
Astrophysics 53, 2015 (submitted)
Gibb EL, Whittet DCB, ApJL 566, 113 (2002)
Herbst E, van Dishoeck EF, Annual Review of Astronomy and Astrophysics, 47, 427
(2009)
Mumma MJ, Charnley SB, Annual Review of Astronomy and Astrophysics 49, 471
(2011)
Schutte WA, Khanna RK, A&A 398, 1049 (2003)
Theule P, Duvernay F, Danger G, et al., Advances in Space Research 52, 1567 (2013)
Kuiper Belts - Cradles of Cosmic Life
Prof. Dr. Ralf I. Kaiser
Department of Chemistry
W.M. Keck Research Laboratory in Astrochemistry
University of Hawaii at Manoa, Honolulu, HI 96822, USA
http://www.chem.hawaii.edu/Bil301/welcome.html
http://www.chem.hawaii.edu/Bil301/KLA.html
Kuiper Belt Objects (KBOs) have emerged in their critical role to understand the chemical evolution of the Solar System and how the molecular precursors to life formed and came together to
create environments such as on early Earth. KBOs are small planetary bodies orbiting the sun beyond the planet Neptune, which are among the least modified, most primitive objects in the Solar
System. A study of KBOs is important because they are keys to understand the evolution of matter in the early Solar System and are considered as ‘natural time capsules’ at a frozen stage
before life developed on Earth. Since dynamical processes exist, which move material residing in
the Kuiper Belt into the inner Solar System, this may well play a role in delivering biorelevant
molecules to early Earth. As KBOs are windows into the dawn of our Solar System, deciphering
the underlying chemistry of KBOs is therefore central to the understanding of the Origins of Life.
In our laboratory, this understanding is achieved by studying the radiation-induced formation of
key classes of biorelevant molecules central to the Origins of Life in ices of Kuiper Belt Objects
(KBOs) from simple precursor molecules (water, methane, ammonia, carbon monoxide, carbon
dioxide, nitrogen, methanol) by reproducing the space environments in a next generation space
simulation chamber. Biorelevant molecules are identified on line and in situ by a unique suite of
tools which have never been assembled together previously. While functional groups of organic
molecules in the condensed phase will be accessible via state of the art infrared, Raman, and
UV/VIS spectroscopy, individual biorelevant molecules formed in the ices are probed via
isomer-selective reflectron time-of-flight mass spectrometry exploiting soft photo ionization with
tunable vacuum ultraviolet light generated via four-wave mixing schemes. Considering that
Kuiper Belts have been observed around stars like Fomalhaut and Vega outside our Solar System
as well, this knowledge can be transferred to extrasolar planetary systems with Kuiper Belt
analog structures thus revolutionizing our understanding of the origin of cosmic life as we know
it and eventually revealing the molecular birthplace of life.
This endeavor comes at an exciting time for space exploration. The New Horizons spacecraft is
currently en route to Pluto (2015), the most prominent member of the Kuiper Belt; the Rosetta
mission is at the very moment orbiting 67P/Churyumov–Gerasimenko – a short period comet
from the Kuiper Belt. Both spacecrafts carry out a search for (precursors of) biorelevant molecules. Since Rosetta’s lander Philae touched down on 67P/Churyumov–Gerasimenko, data on
the molecular composition of the comet’s surface can be directly compared with the inventory of
biorelevant molecules extracted from our experiments thus defining the first inventory of biorelevant molecules, which forms the nucleus for evolution of life in our Solar System billions of
years ago.
FORMATION OF MOLECULES OF ASTROBIOLOGICAL RELEVANCE BY SURFACE
HYDROGENATION REACTIONS UNDER DENSE MOLECULAR CLOUD CONDITIONS
S. Ioppolo1, G. Fedoseev2, T. Lamberts2, 3, H. M. Cuppen3, and H. Linnartz2
1
Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
Sackler Laboratory for Astrophysics, Leiden Observatory, University of Leiden, Leiden NL2300 RA, NL
3
Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen NL6500 GL, NL
2
Fax: +31-(0)71-5275819 / Tel: +31-(0)71-5275804 / Email: [email protected]
The unambiguous identification of nearly 200 molecular species in different astronomical
environments proves that our cosmos is a ‘Molecular Universe’. It is currently accepted that icecovered dust grains play a key role in the chemistry of the interstellar medium. The cumulative
outcome of recent observations, laboratory studies, and astrochemical models indicates that there
is a strong interplay between the gas and the solid phase throughout the process of forming
molecules in space [1, 2]. Small and mainly unsaturated species can be created in the gas phase.
However, surface reaction mechanisms on cold dust grains initiate molecular chemistry through
the formation of H2, and likely dominate the formation of COMs (e.g., sugars and amino acids)
in space. Indeed, interstellar grains provide surfaces on which gas-phase species can accrete,
meet, and react, and to which they can donate excess energy. Therefore, in dense cold clouds, icy
dust grains act both as a molecular reservoir and as sites for catalysis.
In the last decade, laboratory work showed that molecules like H2O, CO2, CH3OH, H2CO,
HCOOH, and NH3 are efficiently formed through non-energetic atom addition reaction on cold
ice grains [3-7]. However, more complex molecule formation has always been thought to be
triggered largely by cosmic ray induced UV photon irradiation, and thermal processing [8]. Here,
I present the first laboratory results on the formation of molecules of astrobiological importance
– hydroxylamine (NH2OH), glycolaldehyde (HC(O)CH2OH), and ethylene glycol
(H2C(OH)CH2OH) – by non-energetic surface hydrogenation of NO and CO containing ices,
respectively [9-13]. These experiments aim at simulating the CO freeze-out stage in interstellar
dark cloud regions, well before thermal and energetic processing become dominant. My talk
reviews the most recent work performed at the Sackler Laboratory for Astrophysics in Leiden
(NL). The experimentally established new reaction pathways are implemented into astrochemical
models to study their impact on the interstellar ice evolution under much longer timescales
(105 yr) than possible in the laboratory.
REFERENCES
[1] Herbst and van Dishoeck 2009, ARAA, 47, 427. [2] Garrod 2013, ApJ, 765, 60. [3] Ioppolo,
Cuppen, Romanzin, van Dishoeck, Linnartz 2008, ApJ, 686, 1474. [4] Ioppolo, van Boheemen,
Cuppen, van Dishoeck, Linnartz 2011, MNRAS, 413, 2281. [5] Fuchs, Cuppen, Ioppolo et al.
2009, A&A, 505, 629. [6] Ioppolo, Cuppen, van Dishoeck, Linnartz 2011, MNRAS, 410, 1089.
[7] Fedoseev, Ioppolo, Zhao, Lamberts, Linnartz 2015, MNRAS, 446, 439. [8] van Dishoeck
and Blake 1998, ARAA, 36, 317. [9] Congiu, Fedoseev, Ioppolo et al. 2012, ApJL, 750, 12. [10]
Fedoseev, Ioppolo, Lamberts et al. 2012, JCP, 137, 4714. [11] Minissale, Fedoseev, Congiu et al.
2014, PCCP, 16, 8257. [12] Ioppolo, Fedoseev, Minissale et al. 2014, PCCP, 16, 8270. [13]
Fedoseev, Cuppen, Ioppolo, Lamberts, Linnartz 2015, MNRAS in press.
Long-lived Coherent Dynamics Induced by Cosmic Microwave Background Radiation
Timur Tscherbul and Paul Brumer
Chemical Physics Theory Group
University of Toronto
Toronto, Ontario, Canada
Fax: 416-978-5325
Telephone: 416-978-3569
Email: [email protected]
Quantum coherences generated in molecules due to excitation by incoherent blackbody radiation
is of considerable interest in a number of research areas. As a means of determining the influence
of the coherence time of the radiation on such processes, we have examined Rydberg atom
excitation by the cosmic microwave background, an environment with the longest coherence
time of any natural radiative process. Resultant theoretical results, obtained by solving nonMarkovian equations of motion with no free parameters, show that the atoms display long lived
quantum coherences and associated quantum beats in fluorescence on the time scale of tens of
picoseconds. An analytic model exposes the dependence of coherent dynamics on the energy
splitting between atomic eigenstates, transition dipole moments, and the coherence time of the
radiation. Experimental detection of the fluorescence quantum beat signal from a trapped
ensemble of 108 Rydberg atoms will be discussed, but shown to be technically challenging at
present. Further studies on model systems show the significance of Fano interferences in
obtaining long lived coherences, particularly in the regime where the molecular level spacing is
smaller than the radiative line width.
References: T. Tscherbul and P. Brumer, Phys. Rev. A 89, 013423 (2014)
T. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)
Energetic Gas-Surface Encounters at Ice and Organic Interfaces
Wenxin Li, G. Langlois, K. Gibson, N. Kautz, D. Killelea and Steven J. Sibener
James Franck Institute & Dept. of Chemistry, University of Chicago, Chicago, IL 60637
Email: [email protected]; Tel: 1-773-702-7193
The interaction of energetic atomic and molecular species with water and ice is of fundamental
importance for astrophysical chemistry, as are the interactions of atomic reagents in reactive
heterogeneous systems. Our initial efforts in ice chemistry, involving both experiment and
numerical simulations, demonstrated that translational energy activates the embedding of Xe and
Kr atoms in the near surface region of ice surfaces [1-3]. These studies revealed a rich palette of
dynamics that are dependent upon the kinetic energy of the gas-surface encounter, the size and
mass of the incident specie, as well as the nature of the ice itself; differing dynamics are seen for
crystalline ice in comparison to amorphous solid water. During the past two years we have
substantially expanded these studies to include the energetic embedding dynamics of molecular
systems, namely CF4 [4] and most recently CO2, with ice interfaces using a combination of in
situ FTIR, scattering, and desorption measurements. CF4 and CO2 with high translational
energies (≥ 3 eV) were observed to embed in amorphous solid water. Just as with Xe and Kr, the
initial adsorption rate is strongly activated by translational energy, with the embedding
probabilities for both molecules being less than that for Kr and Xe. At Ei = 3 eV, the embedding
probability for Xe and Kr is ~5x10-4, for CF4 ~5x10-5, and for CO2 ~10-6. The new CO2/ice
system is of particular interest because of its fundamental role in the Earth’s aqueous,
atmospheric, permafrost, and seabed geosciences, as well as in the interstellar and circumstellar
regions. IR spectra of embedded CO2 reveal two peaks, at ~2341 cm-1, and at 2361 cm-1, which
indicate changes in bonding for the embedded CO2 as well as in the formation of local CO2
dimers or clusters, respectively. These results show that energetic ballistic embedding in ice is a
general phenomenon, and represents a significant new channel by which incident species can be
trapped under conditions where they would otherwise not be bound stably as surface adsorbates.
These findings have implications for many fields including environmental science, trace gas
collection and release, and the composition of astrophysical icy bodies in space. If time permits,
further discussion will also be devoted to the reaction mechanisms that we observe for O(3P)
reacting with saturated [5] and unsaturated/aromatic adsorbed hydrocarbons [6].
1. Energetic Ballistic Deposition of Volatile Gases into Ice, K. D. Gibson, Daniel R. Killelea, James S. Becker,
Hanqiu Yuan, and S. J. Sibener, Chem. Phys. Lett., 531 18-21 (2012).
2. Scattering of High-Incident-Energy Kr and Xe from Ice: Evidence That a Major Channel Involves Penetration
into the Bulk, K. D. Gibson, Daniel R. Killelea, Hanqiu Yuan, James S. Becker, Subha Pratihar, Paranjothy
Manikandan, Swapnil C., Kohale, W. L. Hase, S. J. Sibener, J. Phys. Chem. C, 116, 14264-14273 (2012).
3. Chemical Dynamics Simulations of High Energy Xenon Atom Collisions with the (0001) Surface of Hexagonal
Ice, S. Pratihar, S. C. Kohale, L. Yang, P. Manikandan, K. D. Gibson, D. R. Killelea, H. Yuan, S. J. Sibener, and W.
L. Hase, J. Phys. Chem. C, 117, 2183-2193 (2013).
4. Molecular Interactions with Ice: Molecular Embedding, Adsorption, Detection and Release, K. D. Gibson, Grant
G. Langlois, Wenxin Li, Daniel R. Killelea, and S. J. Sibener; Invited Feature Article - The Journal of Chemical
Physics 141, 18C514/1-10 (2014).
5. Modification of Alkanethiolate Monolayers by O(3P) Atomic Oxygen: Effect of Chain Length and Surface
Temperature, Hanqiu Yuan, K. D. Gibson, Wenxin Li, and S. J. Sibener, J. Phys. Chem. B 117, 4381-4389 (2013).
6. Formation of Stabilized Ketene Intermediates in the Reaction of O(3P) with Oligo(phenylene ethynylene)
Thiolate Self-Assembled Monolayers on Au(111), Wenxin Li, Grant G. Langlois, Natalie A. Kautz, and S. J.
Sibener, J. Phys. Chem. C 118, 15846-15852 (2014).
VUV PHOTOLYSIS OF SOLID METHANE
Bing-Ming Cheng
National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu 30076, Taiwan
Fax:+886-3-5783813/Tel:+886-3-5780281/Email: [email protected]
ABSTRACT
In some space objects, methane is observed at small proportions; for examples, the
concentrations of methane are 1.6, 4.7, and 0.2~1.45 % on Titan, young stellar objects and
comets, respectively. In other astronomical objects, methane exists in clouds like water clouds on
Earth; the cycling of methane clouds condenses methane into lakes or oceans in astronomical
environments, similar to water on Earth. From observations from radar imaging of spacecraft
Cassini on Titan, Stofan et al. discovered more than 75 radar-dark patches attributed to liquid
methane lakes (Nature, 2007, vol. 445, 61); this evidence demonstrates convincingly the
existence of pure condensed methane in astronomical environments. The melting point of
methane is about 90 K; liquid methane freezes in cold outer space where temperatures are less
than 40 K, at which methane is known to exist in a solid form. Photons in vacuum-ultraviolet
light and energetic particles incident on molecular solids analogously induce varied effects in
astrophysical environments. The photolysis of CH4 with vacuum-ultraviolet light undoubtedly
serves as an initial process in the evolution of hydrocarbons in space. With light of wavelength
120-200 nm selected from a synchrotron source, we irradiated samples of solid methane at 3 K.
After irradiation on pure solid methane, four distinct products -- CH3, C2H2, C2H4 and C2H6 –
were identified according to their characteristic infrared absorption lines. The distribution among
these products depended on the wavelength of irradiation. We observed all four products upon
excitation at 121.6, 130 and 140 nm, C2H2 and C2H6 at 155, 165 and 175 nm, and only C2H2 at
185 and 190 nm. No product was observed after irradiation at 200 nm. In contrast, photolysis of
methane dispersed in solid neon at 121.6 nm, at ratios 1:100 to 1:10,000, yielded many more
products, comprising CH3, C2H2, C2H3, C2H4, C2H6, C4H2, C4H4, C5H2 and C8H2, CnH (n=1-5),
and carbon chains Cn (n=3-20); not only the production but also the yield of carbon agglomerates
increased with a decreasing initial concentration of methane dispersed in solid neon. For
example, at CH4:Ne = 1:100, the products with 121.6 nm were stable molecules C2H2, C2H4,
C2H6, C4H2, and radicals CH3, C2H3, C3H, C4H, C5H, C6; whereas, at CH4:Ne = 1:10,000, the 30
products included stable molecules C2H2, C2H4, C2H6, C4H2, C4H4, oxides CO and C5O, hydride
radicals CH, CH3, C2H3, C2H, C3H, C4H, C5H, C5H2, C8H2, and carbon chains C3, C4, C5, C6, C7,
C8, C9, C10, C11, C12, C14, C16, C18, and C20. The photolysis of methane in a solid sample is thus
affected to a large extent by the environment of the methane molecules. The comparison with the
photochemistry of methane dispersed in neon exposes another disparity regarding a dissociation
threshold. No product of photolysis of methane was detectable on irradiation of methane
dispersed in neon at wavelength larger than 150 nm, whereas methane was photolyzed to
produce C2H2 at 190 nm in a pure solid state. A novel finding in our present work is that the
largest wavelengths at which products C2H6, C2H4 and C2H2 were generated were 175, 140 and
190 nm, respectively, through a radiative process: the greatest molecular disruption occurred
with the photons of least energy. Our photochemical experiments on solid methane are thus
directly applicable to space environments. Information about the dissociation of CH4 at low
temperature with photons of varied energy has implications for astrophysical environments.
Formation and Isomer-Specific Detection of Complex Organic Molecules in
Astrophysical Ice Analogs
Matthew Abplanalp, Brant Jones, Ralf Kaiser
Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI 96822
W.M. Keck Research Laboratory in Astrochemistry, University of Hawai’i at Manoa, Honolulu, HI 96822
Email: [email protected]; [email protected]; [email protected]
ABSTRACT
We present results from the W.M. Keck Research Laboratory in Astrochemistry on the formation
of complex organic molecules starting from simple ice mixtures of carbon monoxide (CO) and
simple hydrocarbons (C2H4 or C2H6) upon interaction of the ices with ionizing radiation.
Specifically, a reflectron time-of-flight mass spectrometer coupled with soft vacuum ultraviolet
tunable photoionization was used to discriminate between complex organic isomers, such as
propanal/cyclopropanone (C3H4O) and acetone/propanal (C3H6O). The use of soft tunable
photoionization allows for the parent molecular ion to be produced from sublimed molecules
formed within the processed ice without fragmentation, and also for specific molecules to be
detected based upon their unique ionization energies. Selective isotopologue ices were also used
to unambiguously determine which molecules were formed. Several molecules existing as ices
consisting of H2O, CO, CO2, CH3OH, NH3, and CH4 have been detected in the interstellar
medium and are subject to chemical processing due to galactic cosmic rays, UV photons, and
other forms of ionizing radiation. This research focuses on understanding the evolution of analog
ices by simulating the chemical processing via ionizing radiation in an ultrahigh vacuum
chamber while analyzing the system online and in situ with several spectroscopy methods in the
ice (UV-Vis, FT-IR, Raman) as well as the sublimed gas products during temperature
programmed desorption studies (QMS, ReTOF-PI). These studies can provide a detailed
description of the molecules that are formed from the processing of interstellar analog ices.
Reflectron Time-of-Flight mass spectrum as a function of temperature for the newly formed species from
the energetic processing of carbon monoxide (C18O) – ethylene (C2D4) ice at a photoionization energy of
10.49 eV.
PHOTOIONIZATION DYNAMICS, MOLECULAR GROWTH AND NUCLEATION WITH
MOLECULAR BEAMS AND SYNCHROTRON RADIATION
Biswajit Bandyopadhyay, Yigang Fang, Oleg Kostko & Musahid Ahmed
MS 6R 2100, Lawrence Berkeley National Laboratory, Berkeley, CA-94720
510-486-5311/510-486-6355/[email protected]
ABSTRACT
The photoionization dynamics of clusters is of paramount interest in a number of fields spanning
biology, chemistry, and physics. Understanding the changes in electronic structure that occur in
these ionic clusters is critical to unveil their structure and function and is important in fields as
diverse as cloud nucleation in the earth and planetray atmospheres, radiation biology, and
catalysis. Coupled with electronic structure calculations, photoionization mass spectrometry with
tunable VUV synchrotron radiation provides for insight into diverse processes such proton
transfer in solvated DNA nucleobases,1 fragmentation in strongly hydrogen bonded ionic
systems,2 and elucidation of potential energy surfaces.3 I will discuss this and also highlight new
directions in probing molecular growth and nucleation in ion and neutral cluster systems.
We have recently developed an experimental strategy for characterizing neutral versus ioninduced growth using in-source ionization of molecular beams with tunable VUV synchrotron
radiation. Methanol was chosen as a model system (since our group had extensively studied its
VUV photoionization processes) and by varying the distance between ionization and source, a
new method of studying molecular growth was enabled. The dominant distribution are
protonated methanol clusters (CH3OH)nH+), followed by protonated methanol-water
((CH3OH)n)(H2O)H+) and protonated methanol-dimethyl ether ((CH3)2O(CH3OH)nH+) clusters.
The intensity distributions show signatures for both ion induced and neutral growth, and can be
qualitatively modelled by Thomson’s liquid drop model.4 I will discuss these results and also
show molecular growth processes in acetylene/ethylene clusters.
REFERENCES
1) K. Khistyaev, A. Golan, K. B. Bravaya, N. Orms, A. I. Krylov, and M. Ahmed, “Proton
transfer in nucleobases is mediated by water,” J. Phys. Chem. A., (2013) 117, 6789
2) F. Bell, Q. N. Ruan, A. Golan, P. R. Horn, M. Ahmed, S. R. Leone, and M. Head-Gordon,
“Dissociative Photoionization of Glycerol and its Dimer Occurs Predominantly via a
Ternary Hydrogen-Bridged Ion-Molecule Complex,” J. Am. Chem. Soc., (2013) 135,
14229
3) M. Perera, R. B. Metz, O. Kostko, and M. Ahmed, “Vacuum Ultraviolet Photoionization
Studies of PtCH2 and H-Pt-CH3: A Potential Energy Surface for the Pt + CH4 Reaction,”
Angew. Chem. Int. Ed., (2013) 125, 922
4) B. Bandyopadhyay, Y. Fang, O. Kostko, and M. Ahmed, “In-Source VUV Ionization
Induces Nucleation in a Molecular Beam of Methanol” (To be submitted)
Extended Hydrogen Microwave discharge lamp studies for laboratory applications Niels Ligterink1, Daniel Paardekoper1, Harold Linnartz1 1
Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University In various regions of the interstellar medium, such as cold dark clouds and protoplanetary disks, where cosmic ray induced H2 emission yields vacuum UV photons, ice covered dust grains will undergo photo­induced physical and chemical processes. In the laboratory such light has been simulated for decades using hydrogen microwave discharge lamps. These lamps are intense and cover the range between 115 to 200 nm, specifically Lyman­alfa transitions at 121 nm and several molecular hydrogen transitions around 160 nm. However, in the past years it has become more and more apparent that a more systematic characterization of these lamps is necessary to compare quantitative results from different laboratories [Chen et al. 2014]. Clearly, emission features depend on a number of parameters, such as H2 pressure, gas mixture, MW power, lamp and cavity design. Given the wavelength dependent nature of some processes, such as ice photodesorption [Fayolle et al. 2011] it is important that the parameters determining the lamp operation are fully understood. Here we present new results, confirming findings by Chen et al 2014, but also extending on these, using a vacuum UV spectrometer as available at the Leibniz Institut für Plasmaforschung und Technologie (INP Greifswald) [Foest et al. 2007]. This spectrometer is highly precise both in wavelength and absolute intensity, using a calibrated D2 DC lamp. We will show settings for which the lamp provides a higher output and how to manage the 121/160 band ratios in a way that this helps to interpret photodesorption efficiencies [Öberg et al. 2009, Muñoz­Caro et al. 2010], measured in different groups, in a consistent way. Y.­J. Chen, K.­J. Chuang, G. M. Muñoz Caro et al. 2014, APJ 781:15 E.C. Fayolle, M. Bertin, C. Romanzin et al. 2011, APJL 739:L36 R. Foest, E. Kindel , H. Lange et al. 2007, Contrib. Plasma Phys. 47, No. 1­2, 119 – 128 K.I. Öberg, E.F. van Dishoeck, H. Linnartz, 2009, A&A 496, 281­293 G.M. Muñoz­Caro, A. Jiménez­Escobar, J.Á. Martín­Gago et al. 2010, A&A 511, A108 We thank INP Greifswald (www.inp­greifswald.de) and especially Mr. Holtz for making the measurements presented here possible. Contact or more information: [email protected] Figure 1. Three spectra showing the differences between a lamp running on pure H2 and two lamps running on a H2:He or D2:He mixture. These spectra clearly show the increase in the Lyman­alfa component after helium addition and suppresion of molecular bands. CHEMICAL EVOLUTION OF ASTROPHYSICAL AND PLANETARY ICE ANALOGS
UNDER RADIATION: IN-SITU TWO-COLOR LASER ABLATION AND IONIZATION
MASS SPECTROMETRY (2C-LAIMS)
Bryana L. Henderson and Murthy S. Gudipati*
Ice Spectroscopy Lab, Science Division, Jet Propulsion Laboratory, California Institute of
Technology, Pasadena, CA 91109, USA.
Fax: +1-818-393-4445; Tel: +1-818-354-2637; *E-mail: [email protected]
ABSTRACT
Studying the chemical evolution of ices in the interstellar medium and around stars at different
stages of their lives provides insight into the formation and evolution of complex organics under
radiation and the likelihood of their survival and transport to Earth-like planets.
Traditional spectroscopic methods (ultraviolet, infrared, and fluorescence) have contributed
significantly to enhance our understanding of the evolution of ices and organics in the Universe
(Allodi et al. 2013; Herbst 2014). However, these techniques have some limitations and search
for complementary techniques has begun recently (Gudipati & Yang 2012). Two-color laser
ablation and laser ionization mass spectrometry (2C-LAIMS), demonstrating that chemical
evolution of ices and impurities therein can be monitored by generating plumes of these ices and
subjecting the plumes to multiphoton ionization (MPI), has paved a path for new complementary
methods (Henderson & Gudipati 2014a; Henderson & Gudipati 2014b; Yang & Gudipati 2014).
Other similar works are also emerging to probe and understand the chemistry and composition of
ices (Maity, Kaiser, & Jones 2014; Paardekooper et al. 2014), indicating the importance of timeof-flight mass spectrometry in understanding the chemical evolution of astrophysical and
planetary ice analogs.
In this talk we will discuss the effect of photons vs. electrons on water-rich ices containing the
most common carbon-containing molecule methanol (CH3OH) and nitrogen-containing molecule
ammonia (NH3). We found that even under the coldest temperatures studied (5 K) electron or
photon irradiation of these ices leads to production of several complex organics, many of which
are observed in the interstellar ices as well as in cometary outgassing.
Acknowledgments: This work has been conducted at the Jet Propulsion Laboratory, California
Institute of Technology under a contract with the National Aeronautics and Space
Administration. Funding from NASA Planetary Atmospheres and Cassini Data Analysis
Programs and NASA Postdoctoral Fellowship to BLH is gratefully acknowledged.
References
Allodi, M. A., et al. 2013, SSRv, 180, 101
Gudipati, M. S., & Yang, R. 2012, The Astrophysical Journal Letters, 756, L24
Henderson, B. L., & Gudipati, M. S. 2014a, ApJ, (accepted for publication)
Henderson, B. L., & Gudipati, M. S. 2014b, J Phys Chem A, 118, 5454
Herbst, E. 2014, PCCP, 16, 3344
Maity, S., Kaiser, R. I., & Jones, B. M. 2014, ApJ, 789
Paardekooper, D. M., Bossa, J. B., Isokoski, K., & Linnartz, H. 2014, RScI, 85
Yang, R., & Gudipati, M. S. 2014, J Chem Phys, 140, 104202 (7pp)
FOLLOWING THE CHEMICAL HISTORY OF STELLAR EJECTA THROUGH
ASTRONOMICAL OBSERVATONS AND LABORATORY SPECTROSCOPY
L.M. Ziurys, D.T. Halfen, J.L. Edwards, J. Min, and D.R. Schmidt
Department of Chemistry and Biochemistry, Department of Astronomy and Steward
Observatory, Arizona Radio Observatory, University of Arizona, Tucson, AZ 85721
520-621-5554/520-621-6525/[email protected]
ABSTRACT
Mass loss from circumstellar envelopes of evolved stars and the more advanced, planetary nebulae (PNe)
stage, is a major avenue by which the interstellar medium (ISM) is enriched in gas, dust, and the heavier
elements. The chemical and physical characteristics of circumstellar shells and subsequent PNe thus have
major impact on the overall life cycle of dense material in the ISM, as well as determining Galactic
chemical evolution. Through a combined observational and laboratory program, we have been
investigating the chemistry of such envelopes and the subsequent planetary nebula phase. The laboratory
aspect has centered on high resolution rotational spectroscopy of molecules possibly associated with these
regions, using a combination of direct absorption and Fourier transform microwave/millimeter-wave
(FTMmmW) techniques. Recent studies have included measurements of the CCN (X2Πr), SH+ (X3Σ-), and
ScO (X2Σ+) radicals. Observational work includes searches for these molecules and other species in
circumtellar environments, and in various planetary nebulae, using the telescopes of the Arizona Radio
Observatory. CCN has now been identified in the carbon-rich envelope of IRC+10216 with an abundance
of f0 ~ 6 × 10-8, resulting in a [CN]/[CCN]/[C3N] ratio of ~ 500:1:50. Furthermore, studies of
PNe have resulted in the detection of numerous polyatomic species in older nebulae, including
HNC, SO2, N2H+, H2CO, and CCH, in complete contradiction to model calculations. This result
suggests that some significant fraction of the molecular content of circumstellar shells survives into the
late stages of the PNe phase, and is being recycled into the diffuse ISM. Interstellar molecules therefore
appear to be far more robust than theoretically predicted, and can be abundant in regions thought to be
overwhelmingly atomic in composition.
PHOTOSTABILITY OF ORGANICS IN LOW EARTH ORBIT: RESULTS FROM
SPACE EXPOSURE PLATFORMS AND NANOSATELLITES
Pascale Ehrenfreund1,2, Andreas Elsaesser1, Arthur Stok1, Euan Monaghan1, Richard C. Quinn3,
Antonio J. Ricco4, Andrew L. Mattioda4, Amanda Cook4, Farid Salama4, K. Bryson4, Bernard
Foing5
1
Leiden Observatory, 2300 RA Leiden, NL, 2Space Policy Institute, Washington DC, USA, 3Carl
Sagan Center, SETI Institute, 189 Bernardo Ave, Suite 100, Mountain View, CA, 94043, USA,
4
NASA Ames Research Center, Moffett Field, CA, USA, 5ESA/ESTEC, Noordwijk, NL, email:
[email protected]
ABSTRACT
The study of the reactions, destruction, and longevity of organics in the space environment is of
fundamental interest. To provide an accurate outer space environment for extended durations,
exposure experiments in low Earth orbit have been conducted in the last decades in order to
examine the consequences of actual space conditions including combinations of solar and cosmic
radiation, space vacuum, and microgravity. A series of successful experiments performed on
International Space Station (ISS) external platforms have provided insights into the evolution of
organic and biological materials in space and planetary environments. The O/OREOS
(Organism/ORganic Exposure to Orbital Stresses) nanosatellite studied in situ during the 6month primary and 1-year extended mission the photochemical processing of the PAH
isoviolanthrene, the quinone anthrarufin (1,5-dihydroxyanthrarquinone), and iron
tetraphenylporphyrin chloride in low Earth orbit (650 km altitude); results were autonomously
telemetered to Earth. We report on the methods and flight preparation of samples for space
exposure platforms and results on the stability of organic thin-films. We also present laboratory
experiments investigating the photostability of the anthraquinone derivative anthrarufin and its
interaction with iron oxide thin-films, namely magnetite and hematite. The UV-vis degradation
process of anthrarufin thin-films was recorded over time, which revealed intriguing and counterintuitive photolytic kinetics that will be re-investigated on the ISS in a space environment.
Laboratory Studies of Astronomical Ices at the NASA Goddard Space Flight Center:
Past Successes, Present Efforts, and Future Perspectives
Reggie L. Hudson, Perry A. Gerakines, and Mark J. Loeffler
Astrochemistry Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771
Fax: (301) 286-0440 Tel: (301) 286-6961 Email: [email protected]
Web: http://science.gsfc.nasa.gov/691/cosmicice/
ABSTRACT
NASA has supported an active laboratory research program to study the chemistry and
spectroscopy of astronomical ices for over 30 years at the Goddard Space Flight Center. Our
group's earliest work, and that in the recent past, helped to establish chemical and physical
phenomena in ices that are still being studied and led to predictions later verified by astronomical
observers and expanded upon by others. More specifically, radiation-chemical and spectroscopic
methods have been used to provide insight into the expected evolution of icy materials within
and beyond the Solar System, motivated by potential applications to NASA-related, and NASAfunded, projects.
This presentation will begin with a brief review of our research group's original purpose and
goals, followed by several examples of current research into irradiated ices, such as relate to
Jovian cloud chemistry and Martian astrobiology. Both published and unpublished results will
be presented. In the final part of the presentation the speaker will offer a few brief perspectives
and predictions for the near future of the field.
SELECTED RECENT WORK
Hudson, R. L., Ferrante, R. F., and Moore, M. H. (2014). Infrared Spectra and Optical Constants
of Astronomical Ices: I. Amorphous and Crystalline Acetylene. Icarus, 228, 276-287.
Hudson, R. L. and Loeffler, M. J. (2013). Ketene Formation in Interstellar Ices: A Laboratory
Study. The Astrophysical Journal, 773, 773-782.
Gerakines, P. A., Hudson, R. L., Moore, M. H., and Bell, J-L. (2012). In-situ Measurements of
the Radiation Stability of Amino Acids at 15 - 140 K. Icarus, 220, 647-659.
Loeffler, M., Hudson, R. L., Moore, M. H., and Carlson, R. W. (2011). Radiolysis of Sulfuric
Acid, Sulfuric Acid Monohydrate, and Sulfuric Acid Tetrahydrate and its Relevance to Europa.
Icarus, 215, 370-380.
Peeters, Z., Hudson, R.L., Moore, M.H., and Lewis, A. (2010). The Formation and Stability of
Carbonic Acid on Outer Solar System Bodies. Icarus, 210, 480-487.
VUV spectroscopy of carbonaceous dust analogues relevant
to the interstellar medium
Lisseth Gavilan1*, Ivan Alata1,2, Thomas Pino1,2, Emmanuel Dartois1
1
Institut d’Astrophysique Spatiale (IAS), UMR 8617,
Université Paris Sud, bâtiment 121, 91405 Orsay, France
2
Institut des Sciences Moléculaires d’Orsay (ISMO), UMR 8214,
Université Paris Sud, bâtiment 210, 91405 Orsay, France
*
Email: [email protected]
ABSTRACT
At the IAS and ISMO laboratories (Université Paris Sud, France), we produce analogues to
carbonaceous interstellar dust encountered in various phases of the interstellar medium:
amorphous hydrogenated carbons (a-C:H) and soots. The a-C:Hs were produced using an R.F.
plasma reactor at low pressures, and their structure is dominated by an aliphatic skeleton1. The
soots have been produced in an ethylene (C2H4) flame and provide samples dominated by a
polyaromatic carbon skeleton2.
We have measured thin films (<100 nm) of these analogues in transmission in the far ultraviolet
(190 - 250 nm) and in the vacuum ultraviolet (50 - 190 nm) regions using the DISCO/APEX
beamline of the SOLEIL synchrotron. These materials were also characterized via infrared
microscopy on the SMIS beamline. These measurements enable the derivation of optical
constants and photo cross-sections used to improve models of the photochemistry of these
materials in astrophysical environments. The relation between the IR and UV spectral properties
of these materials and their astronomical counterparts will be discussed.
REFERENCES
1. E. Dartois, G. M. Muñoz Caro, D. Deboffle, et al. « Ultraviolet photoproduction of ISM
dust: Laboratory characterisation and astrophysical relevance » , A&A 432, 895–908
(2005)
2. Y. Carpentier, G. Féraud, E. Dartois, et al. « Nanostructuration of carbonaceous dust as
seen through the positions of the 6.2 and 7.7 µm AIBs », A&A 548, A40 (2012)
WHAT CONTROLS THE DIFFUSION MECHANISM OF HYDROGEN ATOM ON ICE?
Naoki Watanabe, Tetsuya Hama, Kazuaki Kuwahata, Akira Kouchi
Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819,
JAPAN
Email: [email protected]
In molecular clouds, the accretion rate of hydrogen atom on dust is considered to be very low,
something like 1 atom per days, so that the surface number density of H atoms is very limited. In
such a situation, significant surface diffusion of H atoms is necessary to encounter reaction
partners on dust. Therefore, investigating the diffusion mechanism of H atom on ice in various
conditions is indispensable to understand chemical evolution. There have been many reports on
the surface diffusion of H atom on amorphous solid water (ASW). After debate for a period of
years, as long as we understand, some consensus has been reached for the H-atom diffusion on
ASW (see, as a review, refs [1,2]):
1. The ASW surface consists of various adsorption sites with different potential depths, leading
to the distribution of activation barriers for diffusion;
2. Diffusion mechanism on ASW can be represented by classical thermal hopping over the
barriers of ~20 meV at low coverage (<10-2) of H atoms although tunneling diffusion cannot
be excluded;
3. Very shallow potential sites providing the activation barrier of <18 meV for diffusion
dominate the ASW surface.[3]
The above knowledge was derived from H-H recombination rates in TPD experiments or those
estimated from the attenuation of surface H-atoms after given amounts of H atoms predeposited.
In these experiments, the number of H atoms prepared on the surface tends to be low and thus
recombination would require H atoms to diffuse over relatively long distance. It is reasonable to
consider that longer diffusion makes atoms have more chance to be trapped at the deep
adsorption potential sites. In other words, the diffusion rate observed in these experiments would
be limited by the diffusion over the deep sites. We expect that when H atoms locate nearby each
other, those can meet through short diffusion over the dominant shallow sites without trapped in
the deep sites. In such a situation, the diffusion rate and mechanism would appear differently
from previous experiments.
We recently performed a new experiment in which H- or D-atom number densities on ASW and
polycrystalline ice were measured during atomic deposition at various fluxes. In this experiment,
the number density of H (D) atoms on the surface can be changed by the flux deposited. At
higher number densities (higher fluxes), recombination through short-distance diffusion can be
monitored unlike the previous works. Our results demonstrate that the observed diffusion
mechanism (tunneling or thermal) and rates depend on the diffusion length and the morphology
of ice surfaces. During the atomic deposition, the number density of H atoms was found to differ
from that of D atom even though the fluxes are the same. It means that we should be careful to
compare hydrogenation and deuteration rates which have been determined experimentally in
previous works.
[1] T. Hama & N. Watanabe, Chem. Rev. 113, 8783 (2013)
[2] G. Vidali, Chem. Rev. 113, 8762 (2013)
[3] T. Hama, K. Kuwahata, N. Watanabe, A. Kouchi, Y. Kimura, T. Chigai, V. Pirronello, ApJ
757, 185 (2012)
EXPERIMENTAL APPROACHES TO UNDERSTAND NUCLEATION PROCESS VIA
METASTABLE PHASES
Yuki Kimura, Shinnosuke Ishizuka, Kyoko K. Tanaka
Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060–0819,
Japan
[email protected]
ABSTRACT
Nucleation is a process to form stable particles by self-assembly of atoms, molecules or ions
and to overcome a free energy barrier to generate a new surface. Traditionally, it has been
believed that the nucleation process is a result of a valance of attachment and detachment of
growth units into a stable particle. Against the traditional view, recently, non-classical pathway
of the nucleation process has been proposed, e.g., formation via agglomeration of pre-nucleation
clusters or metastable phases such as amorphous [1-3]. However, there is a lots of matters for
debate. In the nucleation process, it passes through the size of meso-scale. We, therefore,
believe physical properties and singular phenomena of nanoparticles must be taken into account
to understand the nucleation process and also formation process of cosmic dust particles.
Nucleation is very difficult to visualize in experimentally because of rapid process in nanoscale. In order to understand the nucleation process, we started new experimental projects based
on following two approaches; (A) Visualization of nucleation processes from a solution by fluidreaction transmission electron microscope (TEM), which can be observe the nucleation process
from a solution in nanometer scale; (B) In-situ observation of temperature and concentration
using an interferometer, and infrared spectra by FT-IR spectrometer during nucleation from a
vapor phase. Here, we show our recent results related to formation and evolution of cosmic dust
particles accompanying with stellar life.
We succeeded to determine physical parameters, surface free energies and sticking
probabilities, of metallic nanoparticles for homogeneous nucleation and show the nucleation
process via metastable phases based on the nucleation environment and nucleation theories [4].
Homogeneous nucleation is only able to occur under very high supersaturation and then the size
of critical nuclei is only several atoms. The nuclei grow as a melt phase and crystallize
stochastically. In case of Mn, both of stable -Mn and metastable -Mn are formed, and the
case of Mg-silicate, amorphous and crystalline phases are obtained in the resulting sample. We
also performed a nucleation experiment of Fe in micro gravity environment using a sounding
rocket and determined the sticking probability, which is as small as 10-4 or less. This value is
significantly lower than ~100 obtained by ground based bulk experiment. In the presentation, we
will show the possible formation scenario of cosmic dust particles around evolved stars.
REFERENCES
[1] Gebauer, D., Volkel, A., Colfen, H. Science, 322 (2008) 1819.
[2] Nielsen, M. H. et al. Science, 345 (2014) 1158.
[3] Kimura, Y. et al. Journal of the American Chemical Society, 136 (2014) 1762.
[4] Kimura, Y. et al. Crystal Growth and Design, 12 (2012) 3278.
Diffusion and Entrapment in Simple Ice Mixtures
Karin I. Öberg
Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA
+1-617-496-9062 / [email protected]
Diffusion of atoms, radicals and molecules inside of and on top of icy grain mantles regulate the
morphology of these ices as well as their chemistry. Together with desorption, ice diffusion
therefore underpins both grain-surface and gas-phase chemical compositions in the dense and
cold regions of the interstellar medium. We have carried out a series of experiments aimed at
characterizing diffusion-driven processes such as segregation, mixing, and entrapment in water
and CO-dominated ices. The experiments are performed under UHV conditions at low
temperatures (down to 10 K) and with thin ices to mimic interstellar condition. In this talk I will
first discuss the observations that have motivated these studies, including ice observations with
Spitzer and new gas-phase compositional studies with ALMA. I will review the empirical
constraints provided by our and other related experiments in terms of time scales and barriers for
different kinds of ice diffusion. These results have been used in concert with theory to isolate and
quantify some of the microscopic processes that ultimately drive the observed macroscopic
changes in ice morphology and composition. I will discuss these constraints and how they can be
implemented in astrochemical models.
VACUUM ULTRAVIOLET PHOTON-STIMULATED FORMATION OF CO2 AT
BURIED ICE:GRAPHITE GRAIN INTERFACES
J. Shi1, G. A. Grieves1, and T. M. Orlando*1, 2
1
School of Chemistry and Biochemistry and 2School of Physics
Georgia Institute of Technology, Atlanta, GA 30332-0400
Phone: (404) 894-4012, [email protected]
ABSTRACT
The vacuum ultraviolet (VUV) synthesis of carbon dioxide on ice-coated graphite and
isotopic labeled
13
C graphite has been examined for temperatures between 40 and 120 K. The
results show that CO2 can be formed at the buried ice:graphite interface with Lyman-α photon
irradiation via reaction of radicals (O and OH) produced by direct photodissociation and
dissociative electron attachment (DEA) of the interfacial water molecules. The synthesized CO2
molecules can desorb in hot photon dominated regions (PDRs) and lost to space when ice coated
carbonaceous dust grains cycle within the protoplanetary disks. Thus, non-thermal formation of
CO2 at the buried ice:grain interface by VUV photons may regulate the carbon inventory during
the early stage of planet formation. This may help explain the carbon deficits in our solar system,
and suggests that a universal carbon deficit gradient may be expected within astrophysical bodies
surrounding center stars.
LABORATORY DETECTION OF HSNO
FORMED BY THE SURFACE REACTION BETWEEN H2S AND NO
Marie-Aline Martin-Drumel1,*, Caroline C. Womack2, Kyle N. Crabtree3, Sven Thorwirth4
and Michael C. McCarthy1
1
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
3
Department of Chemistry, University of California-Davis, Davis, CA 95616, USA
4
I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
*[email protected]
2
ABSTRACT
In the cold regions of the interstellar medium (ISM), many complex gas-phase molecules are
believed to form on the surface of dust grains [1], although the exact mechanisms of dust-to-gasphase chemistry remain subtle. In this regard, thionitrous acid, HSNO, may provide a sensitive
test of dust grain chemistry. While calculations conclude that the gas phase reaction between the
two well-known astronomical compounds H2S and NO [2-3] to yield HSNO is endothermic [4],
much to our surprise we find that this molecule is efficiently formed in our experiment,
presumably on metal surfaces, and then liberated into the gas-phase.
HSNO is a good candidate for detection in the ISM: it is a simple nonorganic molecule composed of four elements which are relatively abundant
in the ISM, it has a favorable partition function, and it has a modestly large
permanent dipole moment of about 1 D. Determination of the HSNO
abundance in space, relative to its more stable isomer HNSO, might provide
a sensitive probe of solid-state versus gas-phase formation.
Here we report the first detection of both cis- and trans-HSNO, by means of
Fourier-transform microwave spectroscopy and double resonance
experiments. Subsequent isotopic studies have enabled a precise molecular
structure determination of both species. Once formed, HSNO appears quite
stable, as evidenced by its high steady-state concentration in our gas
expansion. The global minimum structural isomer of the [H,N,S,O] system,
cis-HNSO, is observed under the same experimental conditions, indicating
some tendency towards rearrangement.
This talk will discuss the HSNO chemistry, the possible formation routes of this molecule, and
more general NO-initiated processes.
REFERENCES
[1] Bisschop S. E. et al. A&A 465, 913 (2007)
[2] P. Thaddeus et al., Astrophys. J. 176, L73 (1972)
[3] H. S. Liszt & B. E. Turner, Astrophys. J. 224, L73 (1978)
[4] G. K. Kolluru et al., Redox Biology 1, 313 (2013)
INFRARED SPECTRA OF PROTONATED SPECIES AND THEIR NEUTRAL
COUNTERPARTS ISOLATED IN SOLID PARA-HYDROGEN
Masashi Tsuge,a) Yu-Jong Wu,b) Yuan-Pern Leea), c)
a)
Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung
University, 1001, Ta-Hsueh Road, Hsinchu 30010, Taiwan
b)
National Synchrotron Radiation Research Center, 101, Hsin-Ann Road, Hsinchu 30076,
Taiwan
c)
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
FAX:+886-3-5713491/Tel:+886-3-5131459/e-mail:[email protected]
Protonated polycyclic aromatic hydrocarbons (H+PAH) have been reported to have infrared
(IR) bands at wavenumbers near those of unidentified infrared (UIR) emission bands from
interstellar objects. However, recording IR spectra of H+PAH in laboratories is challenging. Two
spectral methods are employed to yield IR spectra of H+PAH. One employs IR multiphoton
dissociation (IRMPD) of H+PAH, but the bands are broad and red-shifted.1 Another measures the
single-photon IR photodissociation (IRPD) action spectrum of cold H +PAH tagged with a
weakly bound ligand, such as Ar, but application of this method to large PAH is difficult.2 A new
method for investigating IR spectra of H+PAH and their neutral counterparts was developed
using electron bombardment during p-H2 matrix deposition.
With this technique, we have recorded high-resolution IR absorption spectra of protonated
forms of benzene (C6H7+),3 naphthalene (1- and 2-C10H9+),4 pyrene (1-C16H11+),5 to coronene (1C24H13+)6 and their neutrals. The significant superiority of the spectra recorded with our
technique to those with the Ar-tagging and IRMPD methods is demonstrated. A survey of these
experimental results shows that three major lines in the 79 m region are red-shifted from 7.19,
7.45, and 8.13 m of 1-C16H11+ to 7.37, 7.53, and 8.21 m of 1-C24H13+, showing the direction
towards the UIR bands near 7.6, 7.8, and 8.6 m. In contrast, the line at 11.5 m of 1-C16H11+ is
blue-shifted to 11.4 m for 1-C24H13+, showing the direction toward the UIR band near 11.2 m.
We have also extended this work to ovalene, and the preliminary results indicate that the trend in
spectral shifts is maintained.
We have also investigated small protonated species such as HN2+, HN4+, HCO2+, XeHXe+,
KrHKr+, and KrHXe+. In these cases, p-H2 compete for the proton and results into significant
matrix shifts in spectral bands. Some representative examples will be discussed.
1.
2.
3.
4.
5.
6.
REFERENCES
H. Knorke, J. Langer, J. Oomens, O. Dopfer, Astrophys. J. Lett. 706, L66 (2009).
A. M. Ricks, G. E. Douberly, M. A. Duncan, Astrophys. J. 702, 301 (2009).
M. Bahou, Y.-J. Wu, Y.-P. Lee, J. Chem. Phys. 136, 154304 (2012).
M. Bahou, Y.-J. Wu, Y.-P. Lee, Phys. Chem. Chem. Phys. 15, 1907 (2013).
M. Bahou, Y.-J. Wu and Y.-P. Lee, J. Phys. Chem. Lett. 4, 1989 (2013).
M. Bahou, Y.-J. Wu, and Y.-P. Lee, Angew. Chem. Int. Ed. 53, 1021 (2014).
LABORATORY STUDY AND ASTROPHYSICAL MODEL OF DUST SURFACE
CHEMISTRY IN THE INNER SOLAR NEBULA
Martina D’Angelo1,2, Inga Kamp 2 & Petra Rudolf 1
1.Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The
Netherlands
2. Kapteyn Institute, University of Gronigen, PO Box 800, 9700 AV Groningen, The Netherlands
[email protected]
ABSTRACT
Recent observations have revealed a rich organic chemistry (e.g CO2, C2H2, HCN) in the inner
warm regions of protoplanetary disks around young T Tauri stars1, posing the question to which
extent the gas-grain interaction and the intense star radiation field (X-ray and UV) can favour the
formation of essential organic molecules necessary for the origin of life.
We are investigating the catalytic activity of montmorillonite clay, a natural crystalline
aluminosilicate making up 40% of Earthʼs crust and likely representative of the phyllosilicate
matrix of many meteorites2 and interplanetary dust particles3 (IDPs). Its layered, negatively
charged structure promotes intercalation of polar molecules and formation of organo-silicate
bonds 4. This smectite clay is an excellent water trap thanks to its swelling property5, suggesting
that the clay matrix in meteorites may operate as water reservoir and could catalyze the
formation of oligomers such as pre-RNA, giving new insights on how life originated on Earth6.
In our project we combine a new astrophysical model of the Solar Nebula with laboratory
surface experiments to unravel the mechanisms by which sub-micron-sized silicate dust grains
could have contributed in developing simple organics, trapping and preserving them within their
structure and transporting them throughout the Solar Nebula.
We reproduce the physical conditions of the inner and warm region of a protoplanetary disk,
where dust grain analogues are embedded in 0.01-0.1 mbar of H2/CO/N2 gas mixtures at 250-550
K temperature range, in accordance with the astrophysical disk model ProDiMo7.
Typical surface science techniques such as Reflection-Absorption Infrared Spectroscopy
(RAIRS) together with in situ X-ray Photoelectron Spectroscopy, developed at advanced
synchrotron beamlines, are used to identify reactions products, binding mechanisms and sites.
The empirical results will be used as input parameters for ProDiMo, to study the impact of
catalytic surface reactions on the chemical composition of the inner Solar Nebula.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
Carr J.S., Najita J.R., 2008, Science 319,504.
Pearson, V. K. et al. Meteoritics & Planetary Science 2002, 37: 1829-1833.
Hofmeister, A. M. and Bowey, J.E. Mon.Not.R. Astron.soc. 2006, 367: 577-591.
Kaur, N. and Kishore, D. Journal of Chemical and Pharmaceutical Research 2012, 4: 991-1015.
Schuttlefield, J.D., Cox, D., Grassian, V. H., Journal of Geophysical Research 2007, 112.
Ferris, J.P., Phil.Trans. R. Soc. B 2006, 361: 1777-1786.
Woitke, P., Kamp, I., Thi,W.F. 2009, A&A 501, 383.
Mechanisms of low-energy electron- induced processes in atomic
and molecular solids
Léon. Sanche*
Group in the Radiation Sciences, Department of Nuclear Medicine and Radiobiology,
Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC,
Canada J1H 5N4.
One possible pathway to the formation of the complex organic molecules observed in
astronomical data [1] involves the chemistry engendered by ionizing radiation fields (e.g.,
cosmic rays, X-rays and UV) in icy mantles surrounding the small, micron-sized dust
grains that exist in the interstellar medium (ISM) [2]. Since electrons with energies < 100
eV (i.e., low energy electrons: LEEs), are among the most numerous secondary species
generated by the interaction of ionizing radiation with matter [3], it is likely that
processes initiated by LEEs contribute significantly to the production (and destruction) of
molecular species in the icy mantles. The reactions of LEEs with molecular solids,
similar to those encountered in astrochemical ices, can be studied by irradiating with
energy selected beams of electrons, nanometer-scale molecular solid films constructed at
cryogenic temperatures. The basic mechanisms involved in these reactions are often
different than those of photons, and those found in the gas phase. As in the gasphase[4,5], electron-induced dissociation at energies < 20 eV, which can lead to further
radical reactions and thus the formation of new species, often occur via the formation of
transient negative ions (TNIs) [5]. Yet in addition to TNIs, other basic phenomena
specific to the condensed phase may occur; these include electron-exciton complex
formation and their coupling to TNIs and intermolecular trapping states, breakdown of
electron-molecule symmetry rules, cavity expulsion, cluster reactions, reactive scattering,
coupling of surface states to TNIs and strong density-of-state (DOS) effects on various
electron scattering cross sections [6]. These mechanisms will be explained at the
conference with specific results and a description of the techniques utilized to produce
them. It will be shown that reactions induced at cryogenic temperatures can be very hot
(i.e., they can occur at temperatures well over 10,000 K).
[1] The Cologne Database for Molecular Spectroscopy, HTTP:// http://www.astro.unikoeln.de/cdms/molecules
[2] A. G. G. M. Tielens, Rev. Mod. Phys., 85, 1021 (2013).
[3] S. M. Pimblott, and J. A. LaVerne, Radiat. Phys. Chem., 76 1244 (2007).
[4]. A. D. Bass and L. Sanche, Low Temp. Phys., 29, 202 (2003).
[5] C. R. Arumainayagam, H-L Lee, R. B. Nelson, D. R. Haines, R. P. Gunawardane,
Surf. Sci. Rep., 44 65 (2010)
[6] L. Sanche, Scanning Microscopy, 9619 (1995)
* Tel: 819-821-8000 ext. 74672; e-mail: [email protected]
IMAGE CHARGE DETECTION MASS SPECTROMETRY: APPLICATIONS FROM
ATOMS TO AEROSOLS
Joel Rivera, Katherine A. Nadler, Morgan Miller, Rico Otto and Robert E. Continetti
Department of Chemistry and Biochemistry, University of California, San Diego
9500 Gilman drive, La Jolla, CA 92093-0340
Tel: (858)-534-5559 email: [email protected]
Image Charge Detection Mass Spectrometry (ICDMS) has become a powerful method for nondestructive mass and charge analysis of ionic species. When coupled with a linear electrostatic
ion trap, the mass to charge ratio of an ionic species can be determined by measuring the induced
charge of the ion as it oscillates in the linear electrostatic trap. The m/z of the ion can be
determined from the oscillation frequency, while the charge of the ion is proportional to the
induced charge measurement; the mass of the ion can be determined from these two
measurements. Using the ICDMS technique, mass resolutions on the order of ∆m/m = 10-6 have
been reported for atomic ions.1 Since charged particles are trapped using only electrostatic fields,
ICDMS techniques are not mass limited and can be used for mass analysis of heavier particles.
Measurements of intact viruses with masses on the order of 40MDa have been reported.2 We
have built a Nanoparticle Electrostatic Trap (NET) that will be used for ICDMS studies of
aerosol nanoparticles ejected from a quadrupole ion trap. The performance of this trap on
systems ranging from atomic cations and anions to large (µm) diameter particles will be
reviewed. In addition the interfacing of the NET with the quadrupole ion trap and a subsequent
linear accelerator to allow hypervelocity impact studies of single particles will be discussed.
Acknowledgements: The contributions of Joseph Taulane, Morgan Miller and Clayton Anderson
as well as the support of the NSF MRI program under grant NSF-1229690 are acknowledged.
1. Zajfman D., Rudich Y., Sagi I., Strasser D., Savin D. W., Goldberg S., Rappaport M., Heber, O. Int. J.
Mass Spec., 2003, 229, 55-60
2. Fürstenau S. D., Benner H. W., Thomas J. J., Brugidou C., Bothner B., Siuzdak G. Angew. Chem. Int.
Ed. 2001, 40, 541-544
Thermal reactivity in interstellar ice
Patrice Theulé
Laboratoire de Physique des Interactions Ioniques et Moléculaires
Aix-Marseille University, France
Many reactions involving atoms, radicals, ions or neutrals are taking place in
interstellar ice, increasing the molecular complexity in the interstellar medium.
I will review a particular class of reactions: the purely thermal reactions involving
neutrals.
The small molecules, which are observed in the ice (H2CO, NH3, CO2, …) by infrared
telescopes, can react to form larger molecules.
The kinetics of these rations is dominated both by a large activation energy and by the
diffusion of the reactants.
The corresponding kinetics parameters (activation energy, diffusion coefficients) can
be measured in laboratory and used in gas-grain models
Oxygen chemistry on dust grains
G. Vidali,1 J.He1,2
1
2
Physics Department, Syracuse University, USA
Current address: Chemistry Department, University of Hawai’i at Manoa, USA
(315) 443 3901 [email protected]
ABSTRACT
Oxygen, the third most abundant element in space, intervenes in the formation of many
molecular species, some of which are important in the generation of molecules relevant to the
emergence of life. The realization that many gas-phase processes are insufficient to justify the
abundance of some of these molecules has led to laboratory studies of the formation of
molecules (such as H2O, CO2, and others) on the surface of dust grain analogs in simulated ISM
conditions1,2.
As these surface processes rely on the residence time and diffusion of reactants, we devised a
combination of experiments and theoretical simulations to obtain desorption energy and energy
barriers for diffusion of oxygen atoms and of important oxygen-containing molecules3.
Here we present the results of recent experiments and simulations of the interaction of oxygen
with surfaces of amorphous silicates, amorphous water ice (see figure below), and ammonia
ice4,5. We also report on the formation of water on warm grains6, i.e., grains that are present at
the edge of molecular clouds or of photodissociation regions, and on the formation of precursors
of biogenic molecules5.
temperature
60
32 amu
6000
70
50
4000
16 amu
Temperature (K)
QMS signal (counts/s)
8000
40
2000
30
48 amu
0
0
20
40
60
80
Time (second)
100
120
This work is partially supported by NSF Astronomy & Astrophysics Grant No.1311958.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
G.Vidali, 2013, J. Low Temp. Phys., 170, 1.
T. Hama & N.Watanabe, 2013, Chem. Rev. 113, 8783.
J.He & G.Vidali:, 2014, Faraday Discuss. 168, 5.
J.He, J.Shi, T.Hopkins, G.Vidali & M.Kaufman, 2014, Astrophys. J., submitted.
J.He, G.Vidali, J.L.Lemaire, & R.Garrod, 2014, Astrophys. J., accepted.
J.He & G.Vidali, 2014, Astrophys.J. , 788, 50.
FORMATION OF LARGE ORGANIC MOLECULES ON COSMIC DUST GRAINS
(FROM PREBIOTIC TO AMINO ACIDS MOLECULES)
J. L. Lemaire
Paris Observatory (France)
[email protected]
ABSTRACT
Does life on earth come from interstellar space (IS)? This is a question of paramount interest
involving astrophysics and astrobiology. It has been recently demonstrated that part of the
terrestrial water is of IS origin [1]. This raises the question whether materials like amino-acids or
their pre-biotic molecular precursors could have been formed and brought to earth in the same
way than water. A related question is whether these molecules were formed in the gas phase or
through reactions at the surface or in the volume of ice-covered grains. This may have occurred
in the vicinity of proto-stellar cores in the first case, or, in the second one, deep into a pristine
dense molecular clouds at very low temperatures.
In any case, as far as bio-related molecules are concerned, chemistry with nitrogen-bearing
molecules (like NH3 and NO) is involved. I will review recent experimental work showing that
hydroxylamine (NH2OH) could be formed either by surface or by volume reactions in conditions
close to those prevailing in dense media. They use either electron-UV irradiation of waterammonia ices[2] or successive hydrogenation of solid nitric oxide[3] or the simple oxidation of
ammonia[4] or the reaction of ammonia with hydroxyl radicals in a rare gas matrix[5]. A step
further, the synthesis of the simplest amino-acids, glycine (NH2CH2COOH) and L- or D-alanine
(NH2CH3CHCOOH) has already been obtained via reactions in the gas phase involving
NH2OH+[6].
In addition to several earlier models demonstrating that the formation of all these molecules
is possible in the gas phase, a new recent three-phase gas-grain chemical kinetics model of hot
cores[7] shows that the results of ammonia oxidation obtained in [3] are plausible by
surface/volume reactions.
Although none of the aforementioned molecules (except glycine in a sample of cometary
origin) has been yet detected in the IS, they all are considered by many observers and modelers
as likely targets of detection with ALMA. A short review of the present observational status will
be presented and suggestions of conditions for future observations will be provided.
REFERENCES
[1] Cleeves L.I., Bergin E.A., C.M.O'D., Du F., Graninger D., Öberg K., Harries T.J. 2014, Science, 345,.1590
[2] Zheng W. & Kaiser R.I., J. Chem. Phys. A, 114, 5251, 2010
[3] Congiu E., Fedoseev G., Ioppolo S., Dulieu F., Chaabouni H., Baouche S., Lemaire J.L.,Laffon C., Parent Ph.,
Lamberts, T. Cuppen H.M., Linnartz H. ApJ Letters, 750, L12,.2012
[4] He J., Vidali G., Lemaire J.L., Garrod R.T. ApJ, 2015 (in press)
[5] Zins, E. L., & Krim, L. 2014 (in press) in 69th International Symposium on Molecular Spectroscopy
(http://isms.illinois.edu)
[6] Blagojevic V., Petrie S., Bohme D.K. Mon. Not. R. Astron. Soc., 339, L7, 2003
[7] Garrod, R.T. 2013, ApJ, 765, 60
Reactions of Hydrogen Atoms in Solid Parahydrogen: New Lessons to be Learned
Fredrick M. Mutunga, Morgan E. Balabanoff, David T. Anderson
Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, USA
[email protected]
Our group has been studying a number of H-atom reactions in solid parahydrogen over the
temperature range between 1.7 and 4.3 K. The H-atoms are generated by the 193 nm in situ
photolysis of precursor molecules trapped in the parahydrogen crystal and the subsequent
reaction kinetics are followed using rapid scan FTIR spectroscopy. One of the unique properties
of H-atoms in solid parahydrogen is the H-atom diffusion rate is facile even at temperatures
below 2 K. The delocalized nature of H-atoms in solid parahydrogen therefore permits a variety
of H-atom reactions to be studied within the “deep-tunneling” regime. One of the first reactions
that we studied is the H+NO → HNO reaction which has been studied previously at low
temperature in solid parahydrogen [1] and in interstellar ice analogs [2]. This barrierless radicalradical reaction proceeds at the diffusion limit over the full temperature range studied. However,
we also observe the competing H+NO → NOH reaction which is calculated [3] to have a
significant barrier (6200 K). Furthermore, we have studied the reactions of H-atoms with N2O,
HCOOH, and CH3OH and have measured somewhat surprising kinetics; all these reactions only
occur at an appreciable rate below a critical temperature of around 2.7 K. We have tried to
understand these kinetic results [4] using a two-step reaction mechanism that involves formation
of an encounter complex of the reactants followed by dissociation or reaction, but cannot
quantitatively model our results. In this talk, I will present results from our laboratory and
modeling studies that focus on the contrasting H-atom reaction kinetics measured for NO and
N2O.
References
[1]. M. Fushitani, T. Momose, “A Study on Diffusion of H Atoms in Solid Parahydrogen,” Low
Temp. Phys. 29, 740-743 (2003).
[2]. E. Congiu, et al., “NO Ice Hydrogenation: A Solid Pathway to NH2OH Formation in
Space,” Astrophys. J. 750, L12.1-4 (2012).
[3]. U. Bozkaya, J.M. Turney, Y. Yamaguchi, H.F. Schaefer III, “The Lowest-Lying Electronic
Singlet and Triplet Potential Energy Surfaces for the HNO–NOH System: Energetics,
Unimolecular Rate Constants, Tunneling and Kinetic Isotope Effects for the Isomerization
and Dissociation Reactions,” J. Chem. Phys. 136, 164303.1-15 (2012).
[4]. Fredrick M. Mutunga, Shelby E. Follett, David T. Anderson, “Communication: H-atom
reactivity as a function of temperature in solid parahydrogen: The H+N2O reaction,” J.
Chem. Phys. 139, 151104.1-4 (2013).
The Effects of Temperature on the VUV Photodesorption of CO2 Ice
Y.-J. Chen1, S.-R. Wu1, G. M. Muñoz Caro2, M. Nuevo3,4, C.-C. Chu1, T.-S. Yih1,
W.-H. Ip5, and C.-Y. R. Wu6
1
Department of Physics, National Central University, Jhongli City, Taoyuan County 32054,
Taiwan
2
Centro de Astrobiología, INTA-CSIC, Torrejón de Ardoz, 28850 Madrid, Spain
3
NASA Ames Research Center, Moffett Field, CA 94035, USA
4
BAER Institute, Petaluma, CA 94952, USA
5
Graduate Institute of Astronomy, National Central University, Jhongli City, Taoyuan County
32049, Taiwan
6
Space Sciences Center and Department of Physics and Astronomy, University of Southern
California, Los Angeles, CA 90089-1341, USA
+886-3-4227151 ext 65390/[email protected]
In this study, we present results from experiments in which CO2 ice was deposited and
VUV irradiated at different temperatures, in order to understand the effects of
temperature on the VUV photodesorption yield and to elucidate the mechanism of
VUV-induced photodesorption of CO2 ice. A quartz crystal microbalance (QCM) and
a Fourier-transform infrared (FTIR) spectrometer were used to measure the
photodesorption yield in two separated experimental vacuum systems, each equipped
with a quadrupole mass spectrometer (QMS) to characterize species desorbed during
the experiments.
The results from the QBM show that the photodesorption yield of CO2 ice deposited
and irradiated at 50 K and 70 K increases almost by an order of magnitude higher
with respect to the value at 14 K. The likely explanation is that photodesorption
occurs only on the top few monolayers of CO2 ice at 14 K, whereas CO and O2 can
desorbed from deeper monolayers of CO2 ice at temperatures above 30 K and 50 K,
respectively. On the other hand, mass spectra show that desorbed molecules mostly
originate after photodissociation of CO2 forming CO which photodesorbs, but also
photodesorption of C, O, CO2, and O2 was observed. The desorption rate of O2
increases rapidly when the deposition temperature of CO2 ice is above 50 K. In the
case of CO2 ice deposition and irradiation above 50 K, CO desorbs after the VUV
irradiation is stopped, the maximum mobile distance of CO and O2 molecules in CO2
ice was estimated at 50 K and 70 K.
A BROADBAND (0.3 – 7.5 THz) TERAHERTZ TIME-DOMAIN SPECTROMETER FOR
THE STUDY OF ASTROPHYSICAL ICE ANALOGS
Brett A. McGuire1,2, Sergio Ioppolo3, Marco A. Allodi2, Xander de Vries4, P. Brandon Carroll2,
and Geoffrey A. Blake2,5
1
National Radio Astronomy Observatory
2
Division of Chemistry and Chemical Engineering, California Institute of Technology
3
Department of Physical Sciences, The Open University
4
Radboud University Nijmegen
5
Division of Geological and Planetary Sciences, California Institute of Technology
[email protected] // Office (626) 395-6791
We have previous reported at this meeting on the initial construction of a broadband (0.3 – 7.5
THz) TeraHertz time-domain spectrometer to study condensed-phase samples of astrophysicallyrelevant species. Despite the critical role these species play in interstellar chemical reactions and
evolution, and the wealth of observational facilities available or coming online in the THz,
literature spectra for such species in this spectral window are discouragingly sparse. Here, we
report on the continued design and construction of this spectrometer. Recent upgrades have
improved the sensitivity and resolution of the spectrometer by more than an order of magnitude.
We will report on a number of the first studies enabled by these new capabilities, including
systematic studies of increasingly complex organic molecules, newly observed transitions of
primary ice constituents (e.g., CO2), and polycyclic aromatic hydrocarbons. We find the spectra
to be extremely structure-dependent, and sensitive largely to long-range, large-amplitude
motions within the ices. We will discuss the feasibility of the interstellar detection of species
from these spectra, approaches to the direct determination of optical constants, upcoming proofof-concept observations with the SOFIA telescope, and the challenges associated with comparing
our spectra to theoretical calculations.
Formation of Dust under Astrophysical Conditions
Thomas Henning
Max Planck Institute for Astronomy
Koenigstuhl 17, 69117 Heidelberg, Germany
[email protected]
The lecture will review our knowledge about stellar dust sources in space, ranging from AGB
stars to supernovae. I will discuss the problem of efficient dust destruction and highlight the
possibility of dust formation in the general interstellar medium. In the second part of my talk
I will present the results of dedicated laboratory experiments to study dust formation under
astrophysical conditions.
PRODUCTION OF OPEN-CHAIN PHOSPHANES AND ALKYL-PHOSPHINES IN
ASTROCHEMICAL ICE ANALOGUES
Andrew M. Turner, Matthew J. Abplanalp, Ralf I. Kaiser
Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, United States
W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI
Email: [email protected], [email protected], [email protected]
ABSTRACT
The existence of phosphine (PH3) has recently been confirmed in the carbon-rich circumstellar
envelop of IRC +10216, which along with CP comprise the only phosphorus-containing
molecules discovered around this star. Methane (CH4) and acetylene (C2H2) were the first two
simple hydrocarbons detected around IRC +10216; furthermore, solid-state methane is known to
exist in the interstellar medium. We present results from the W. M. Keck Research Laboratory in
Astrochemistry that study the possible formation products of phosphine that enters the condensed
phase with methane. Phosphine and phosphine-methane ices were irradiated at 5.5 K in ultrahigh vacuum conditions to produce various larger phosphorus hydrides and alkyl-phosphines.
Reflectron time-of-flight mass spectrometry using 10.49 eV vacuum ultraviolet photoionization
proved to be the most sensitive detection method, capable of detecting compounds with greater
than nine phosphorus atoms. Infrared spectroscopy and quadrupole mass spectrometry were also
utilized, but these detected molecules with three phosphorus atoms or fewer. These tools
monitored the ices during temperature-programmed desorption from 5.5 to 300 K. The irradiated
ice analogues simulate the conditions of astrochemically relevant environments, enhance the
knowledge of phosphorus chemistry in the interstellar medium, and provide a list of possible
compounds that may be detected in circumstellar or interstellar media. Looking forward, these
products may be an intermediate to the formation of alkyl phosphonic acids, which were the only
phosphorus-containing organic molecules found in the Murchison meteorite.
Reflectron time-of-flight mass spectrum showing the sublimation products of phosphine
irradiation during warm-up from 5.5 to 300 K.
Methane ice photochemistry and kinetic study using laser desorption time-of-flight
mass spectrometry at 20 K
Jean-Baptiste Bossa, Daniel Paardekooper, Karoliina Isokoski, and Harold Linnartz
Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, The Netherlands
Advances in telescope and interferometer arrays have highlighted a rich and exotic chemistry
occurring in the surroundings of star-forming regions, as evidenced by the detection of more than
180 molecules and ions in space. Complex organic molecules (> 6 atoms) have been
unambiguously detected, but their formation mechanism and corresponding yields are still
unknown. Following astronomical observations, laboratory studies and models, it has become clear
that surface chemistry on icy grains steadily increases the chemical diversity and offers a way to
explain the molecular complexity in space. So far, systematic experimental investigations on the
formation of complex organic molecules have been restricted, mainly due to the limitations imposed
by standard solid-state techniques. To overcome these limitations, a new experimental setup as been
designed.
A new ultra-high vacuum experiment is described that allows studying photo-induced chemical
processes in interstellar ice analogues. MATRIICES: a Mass Analytical Tool to study Reactions in
Interstellar ICES applies a new concept by combining UV laser desorption and time-of-flight mass
spectrometry with the ultimate goal to characterize in situ and in real time the solid state evolution
of organic compounds upon VUV photolysis for astronomically relevant ice mixtures and
temperatures
The performance of the experimental setup is demonstrated by the kinetic analysis of the different
photoproducts of pure methane (CH4) ice at 20 K. A quantitative approach provides molar fractions
at the different stages of the VUV irradiation. These data are then kinetically fitted to a reduced
chemical reaction network in order to obtain the rate constants and ultimately the branching ratios
of photochemical reactions yielding new species with up to two carbon atoms (C 2Hx and C3Hy).
Convincing evidence is found for the formation of even larger species.
INTERSTELLAR AND OUTER SOLAR SYSTEM SOLIDS IN THE LABORATORY
E. Dartois 1,2, I. Alata,3,1,2, Karine Beroff 3, N. Bardin4, R. Brunetto1,2, Marin Chabot5,6, B.
Crane1,2, Gustavo A. Cruz-Diaz7, L. Delauche4, P. Dumas8, J. Duprat4, C. Engrand4, Lisseth
Gavilan1,2, Aurelie Jallat5,6, F. Jamme8, G. Morinaud1,2, S. Mostefaoui9, Guillermo M. Muñoz
Caro7, T. Pino3, E. Quirico10, L. Remusat9, Ch. Sandt8, N. Szwec1,2
1
CNRS-INSU, Institut d'Astrophysique Spatiale, UMR 8617, 91405 Orsay, France
Université Paris Sud, Institut d'Astrophysique Spatiale, UMR 8617, bât 121, 91405 Orsay, France
3
Institut des Sciences Moléculaires d’Orsay (ISMO), UMR 8214-CNRS Université Paris Sud, bât.210, F-91405 Orsay Cedex, France
4
Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud, UMR 8609-CNRS/IN2P3, F-91405 Orsay, France
5
CNRS-IN2P3, Institut de Physique Nucléaire d’Orsay, UMR8608, 91406 Orsay, France
6
Université Paris Sud, Institut de Physique Nucléaire d’Orsay, UMR8608, IN2P3-CNRS, bât 103, 91406 Orsay, France
7
Centro de Astrobiologa (CSIC-INTA), Carretera de Ajalvir, km 4, Torrejon de Ardoz, 28850 Madrid, Spain
8
Synchrotron SOLEIL, L’orme des Merisiers, BP 48, Saint Aubin, F-91192 Gif sur Yvette, France
9
Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) - Sorbonne Universités - UMR 7590 CNRS, UPMC, IRD,
Muséum National d’Histoire Naturelle, 61 rue Buffon, F-75005 Paris, France
10
UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274, F-38041 Grenoble, France
2
EMAIL/[email protected]
ABSTRACT
The interstellar medium is a physico-chemical laboratory where extreme conditions are
encountered, and whose environmental parameters (e.g. density, reactant nature, radiations,
temperature, time scales) define the composition of matter.
Whereas cosmochemists can spectroscopically examine collected extraterrestrial material in the
laboratory [e.g. 1,2,3,4,5], astrochemists must rely on remote observations to monitor and
analyze the physico-chemical composition of interstellar solids [e.g. 6,7,8,9,10].
The observations give essentially access to the molecular functionality of these solids, rarely to
elemental composition constraints and isotopic fractionation only in the gas phase. Astrochemists
bring additional information from the study of analogs produced in the laboratory, placed in
simulated space environments.
In this presentation, recent advances from laboratory experiments will be presented, setting
constraints on the composition of organic solids and molecules in the cycling of matter in the
Galaxy. One objective will be to draw some commonalities and differences between materials
found in the Solar System and Interstellar dust.
This talk will particularly focus on two carbonaceous dust materials, from the far (ISM) and near
(Solar System) space environments: (i) the small species released by the VUV irradiation of
interstellar a-CH analogues and their influence on PDR regions composition [11]; (ii)
extraterrestrial collected dust, Ultracarbonaceous Antarctic Micrometeorites (UCAMMs) from
the CONCORDIA collection [12], associated with the outer Solar System icy bodies.
REFERENCES
[1] Orthous-Daunay et al. (2013) Icarus 223, 534–543. [2] Brunetto et al. (2011) Icarus 212,
896–910. [3] Kebukawa et al. ( 2011) Geochim. Cosmochim. Acta 75, 3530–3541. [4] Sandford
et al. (2006) Science 314, 1720–1724. [5] Flynn et al. (2003) Geochim. Cosmochim. Acta 67,
4791–4806. [6] Spoon et al. (2007) The Astrophysical Journal 654, L49-L52 [7] Dartois &
Muñoz Caro (2007) Astronomy and Astrophysics 476, 1235-1242 [8] Van Diedenhoven et al.
(2004) The Astrophysical Journal 611, 928-939. [9] Chiar et al. (2002) The Astrophysical
Journal 570, 198-209. [10] Pendleton et al. (1994) The Astrophysical Journal 437, 683-696. [11]
Alata et al. (2014). [12] Dartois et al. (2013) 224, 243–252.
Laboratory studies of fundamental transient molecules containing 2nd-row elements
1
Sven Thorwirth1, Valerio Lattanzi2, Jürgen Gauss3, Ralf I. Kaiser4,
Kyle N. Crabtree5, and Michael C. McCarthy6
I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
3
Institut für Physikalische Chemie, Universität Mainz, 55099 Mainz, Germany
4
Department of Chemistry, University of Hawai’i at Manoa, Honolulu, Hawaii 96822, United States
5
Department of Chemistry, University of California - Davis, Davis, CA 95616, United States
6
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States
2
[email protected] / phone: +49-221-470-1936
ABSTRACT
More than 175 astronomical molecules are now known, the vast majority detected by means of
radio astronomy. Although those containing elements from the first row are most frequently
observed in space, we are arguably entering the golden age of interstellar inorganic chemistry,
because larger and more sensitive single-dish telescopes and interferometers have recently come
on-line, and because of the availability of precise rest laboratory frequencies for many small
molecules containing a second-row element or metal atom. Studies of these types of molecules
in the gas phase are crucially important because they ultimately may provide key information on
the formation and destruction of interstellar dust. In this regard, silicon-bearing molecules play a
major role as gas-phase silicon monoxide, SiO, for example is thought to be created in the ISM
from grains subjected to shocks [1]. In turn, grains may form in the same environment from
condensation processes involving SiO [2].
In the laboratory astrochemistry group in Cambridge, a long-term program has been undertaken
to systematically characterize new molecules that are derived from well-known and abundant
astronomical ones, in which one or more atoms are replaced with their second-row counterpart.
The pure rotational spectra of many such species have now been detected, including silanethione,
H2SiS [3] (formally derived from H2CO), HPSi [4] (HCN/HNC), HCCNSi (HCCCN), SiH3SH
(CH3OH), OSiS [5] (OCS/CO2) and HPCO/HNSiO [6] (HNCO). In nearly every instance,
detection was accomplished by means of Fourier transform microwave spectroscopy guided by
high-level quantum level calculations performed at the coupled-cluster level of theory.
This talk will provide an overview of our recent work in this area, and a discussion of the
prospects for future laboratory and radio astronomical studies.
REFERENCES
[1] Schilke, Walmsley, Pineau des Forets, and Flower 1997, Astron. Astrophys. 321, 293
[2] Krasnokutski, Rouille, Jäger, Huisken, Zhukovska, and Henning 2014, Astrophys. J. 782, 15
[3] Thorwirth, Gauss, McCarthy, Shindo, and Thaddeus, Chem. Commun. 2008, 5292
[4] Lattanzi, Thorwirth, Halfen, Mück, Ziurys, Thaddeus, Gauss, and McCarthy 2010, Angew. Chem. Int. Ed. 49, 5661
[5] Thorwirth, Mück, Gauss, Tamassia, Lattanzi, and McCarthy 2011, J. Phys. Chem. Lett. 2, 1228
[6] Thorwirth, Lattanzi, and McCarthy 2014, submitted.
Polycyclic aromatic hydrocarbons as catalysts for interstellar
chemical complexity
L. Hornekær
Dept. Physics and Astronomy, Aarhus University,
Ny Munkegade Bygn. 1520, 8000 Aarhus C, Denmark
*[email protected]
Even though Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous in the interstellar
medium, the role they play as catalysts for interstellar chemistry is still not well
understood. However, existing experimental data [1-3] and theoretical calculations [4]
indicate that PAHs may well play a very active role, in particular in connection with the
formation of molecular hydrogen. These findings may explain observations of increased
molecular hydrogen formation rates in Photodissociation regions with high PAH
abundances [5-6]. In my talk I will present temperature programmed desorption data
demonstrating the formation of highly super-hydrogenated PAHs via hydrogen addition
reactions and catalytic formation of molecular hydrogen via abstraction reactions at a
wide range of H atom temperatures [1-3]. Approximate cross-sections for these
reactions derived via model simulations will be presented [7]. The implications for the
role played by PAHs in interstellar chemistry will be discussed.
[1] J. D. Thrower, E. E. Friis, A. L. Skov, B. Jørgensen and L. Hornekær. Phys. Chem. Chem. Phys. 16, 3381
(2014)
[2] J. D. Thrower, B. Jørgensen, E. E. Friis, S. Baouche, V. Menella, A. C. Luntz, M. Andersen, B. Hammer,
and L. Hornekær. Astrophysical Journal 750, 1, (2012)
[3] V. Menella, L. Hornekær, J. Thrower and M. Accolla. Astrophys. J. Lett. 745, L2 (2012)
[4] E. Rauls and L. Hornekær. Astrophys. J. 679, 531 (2008)
[5] E. Habart, F. Boulanger, L. Verstraete, G. P. des Fortes, E. Falgarone and A. Abergel, Astron. Astrophys.
397, 623 (2003)
[6] E. Habart, F. Boulanger, L. Verstraete, C. M. Walmsley and G. P. des Forets, Astron. Astrophys. 414, 531
(2004)
[7] A. L. Skov, J. D. Thrower and L. Hornekær. Faraday Discussions 168, 223 (2014)
A Mass-analytical Study of UV Irradiated Interstellar Ice
Daniel M. Paardekooper, Jean-Baptiste Bossa, Karoliina Isokoski and Harold Linnartz
Sackler Laboratory for Astrophysics, Leiden University, Leiden Observatory, the Netherlands
With ALMA surveying the inter- and circumstellar medium, it is expected that the number of
new molecules observed in space – more than 180 by now - will increase rapidly. This further
highlights the rich chemistry in star-forming regions. The underlying formation pathways,
however, are not well understood. Decades of astronomical observations, laboratory studies and
astrochemical models point towards a complex interplay between gas-phase and solid state
processes. Many of the larger species are expected to form on icy dust grains, following thermal
processing, irradiation by UV photons or X-rays or bombardment by atoms, electrons and
cosmic rays. In order to characterize these processes under fully controlled conditions, dedicated
laboratory experiments are needed.
Initially, complex ice mixtures were processed, quite often over long periods, and resulting
residues were investigated ex situ. The last decade ultra high vacuum techniques in combination
with RAIRS and/or TPD allow to study chemical processes in ices in situ. The two techniques,
however, are limited in their application; typically species with less than 10 atoms are studied.
Here we introduce MATRIICES [1], a new measurement concept that aims at studying the
formation pathways of larger species (>10 atoms) in photo-processed interstellar ice analogues,
by applying soft-laser ablation combined with time-of-flight mass spectrometry. Interstellar ice
analogues are first grown onto a cold gold substrate (20 K). Surface reactions are induced using
vacuum UV irradiation with a microwave powered H2-discharge lamp, producing Ly-α photons.
In the past CH3OH was already shown to be an excellent starting point for the formation of
complex molecules.[2] MATRIICES extends on this work.
In this talk, the performance of MATRIICES is discussed and data are presented for different
ices. Besides for methanol, also data for methane are presented. During UV irradiation, the
formation and destruction of different hydrocarbons is tracked. A quantitative approach provides
formation yields of several new species with up to four carbon atoms. Convincing evidence is
found for the formation of even larger species. [1,3]
References:
[1] D.M. Paardekooper, J.-B. Bossa, K. Isokoski, H. Linnartz, Laser desorption time-of-flight
mass spectrometry of ultraviolet photo-processed ices, 2014, Rev. Sci. Instrum. 85, 104501.
[2] K. I. Oberg, R. T. Garrod, E. F. van Dishoeck, H. Linnartz, Formation rates of complex
organics in UV irradiated CH3OH-rich ices I: Experiments, 2009, A&A 504, 891.
[3] D.M. Paardekooper, J.-B. Bossa, K. Isokoski, H. Linnartz, in preparation.
PHOTODETACHMENT STUDIES OF NEGATIVE IONS
D. Hanstorp
Department of Physics
University of Gothenburg
SE-412 96 Gothenburg, Sweden
[email protected]
ABSTRACT
The extra electron in a negative ion does not experience the Coulomb force from the nucleus at
large distances. Instead, core polarization induced by the extra electron stabilizes the ion. As a
consequence, the binding energies of negative are typically an order of magnitude smaller than
the ionization potential for neutral systems. Further, the number of excited states is very limited
and normally only the ground state is bound. Hence, traditional optical spectroscopy cannot be
used to investigate negative ions. However, recent interstellar observations of negative ions
have shown that bound-bound transitions can be used to detect negative ions. This has triggered
an intense search for negative ions in interstellar media as well as in corresponding laboratory
experiments.
I will review various laboratory experiments of negative ions. Optical photodetachment spectra
have been measured at the negative ion beam facility GUNILLA in Sweden, using infra-red,
visible and UV lasers. This has yielded information about electron affinities, fine structure
splittings and isotope shifts. Femtosecond spectroscopy has been performed using a velocity
map imaging spectrometer, and the first data from an angular resolved collinear electron
spectrometer will be reported. Further, the first experiment using the newly commissioned
cryogenic electrostatic double storage ring DESIREE, in which the life time of an excited state
in S- has been measured, will be presented. DESIREE is designed to study mutual neutralization
of negative and positive ions at conditions that resembles the environment in the interstellar
media.
A NEW LABORATORY FOR MM-WAVE CHARACTERIZATION OF COSMIC DUST
ANALOGS
Thushara Perera
Illinois Wesleyan University
[email protected]
ABSTRACT
A custom experimental setup has been constructed for measuring the temperature-dependent
absorptivity of cosmic dust analogs, with the hope of providing input for millimeter-wave
observations of dusty environments. A unique feature of this apparatus is that all of its
components—a 4-K cryostat, bolometer + optics, cold sample holder/exchanger, and Fourier
transform spectrometer (FTS)—were designed specifically for laboratory studies of dust
candidates. Some of the main concerns addressed by the instrumentation are: accurate
temperature control (between 5-50 K) of samples and ease of switching between samples,
compactness of cold chamber as well as external FTS (using a novel FTS design), minimization
of optical windows in measurement scheme, use of mm-wave observational techniques to
minimize optical and thermal systematics, and simplicity of operation (catered to undergraduate
students) once completed. We have also started a dust synthesis effort locally, based on sol-gel
methods. The measurement scheme as well as preliminary data on in-house and external (from
NASA Goddard) dust samples will be presented.
CHAIN ELONGATION REACTIONS OF CYANO IONS WITH HYDROCARBONS
P.Fathi,1 F. Lindén,1 D. Ascenzi2 and W. D. Geppert1
Physics Department, Roslagstullsbacken 21, S-10691 Stockholm, Sweden
Dept. of Physics, University of Trento, via Sommarive 14, I-38100 Trento, ITALY
[email protected]
A multitude of large anions and cations has been detected in Titan’s ionosphere by the CassiniHuygens mission [1,2], but their identity and their formation pathways are still elusive in many
cases. However, ion-molecule-neutral reactions followed by dissociative recombination could be
important routes to complex species. The ion–neutral mass spectrometer (INMS) has identified a
number of ion masses corresponding to protonated nitriles and other nitrogen-containing ions
[2]. In addition, the CN-, C3N-, and C5N- anions have been detected by the electron plasma
spectrometer (EPS) on board the Cassini spacecraft. Thus, ions containing cyano groups can be
expected to play a substantial role in the chemistry of Titan’s ionosphere.
Reactions of these ions with unsaturated and saturated hydrocarbons could lead to larger ionic
species, since such processes can be barrier-less and thus feasible at the temperatures prevailing
in Titan’s ionosphere. Mutual neutralization reactions between cations and anions or dissociative
recombination (in the case of cations) can then lead to heavy neutral molecules. However, quite a
number of the detected cations possessing cyano groups are protonated nitriles, which are fairly
unreactive and are mainly destroyed by dissociative recombination. Nevertheless, exceptions like
the CH2CN+ ion exist.
We investigated the reactions of the CH2CN+ ion with a multitude of saturated and unsaturated
hydrocarbons (C2H2, C2H4, CH4 etc.) using the guided ion beam device at the university of
Trento, Italy in order to determine the products and cross-sections of these processes and to
establish if they are feasible pathways for building up entities with longer carbon and carbon
nitrogen chains. Furthermore, the reactions of C3N- with ethylene and acetylene have also been
studied. Experiments using deuterated isotopologues as well as ab initio calculations on the
MP2/6-311G++** level have been employed to explain the obtained findings.
REFERENCES
[1] V. Vuitton, P. Lavvas, R.V. Yelle, M. Galand, A. Wellbrock, G.R. Lewis, A.J. Coates, J.-E.
Wahlund, Planet. Space Sci. 57, 1558 (2009)
[2] V. Vuitton, R. V. Yelle, M. J. McEwan, Icarus, 191, 722 (2007)
Understanding Interstellar Ices, from Molecular Structure
to the Nano- Meso- and Micro- Scales
H.J. Fraser 1 , O. Auriacombe1, A. Dawes1, P. Elkind1, S. Gaertner1, C. Hill1, N. Pascual1,
A. Suutarinen1, D. Chakarov2, J. Noble3, D. Bowron4, B. Ellison4, T. Youngs4, T. Loerting5
1
Astronomy Division, Department of Physical Sciences, The Open University, Walton Hall, Milton
Keynes, MK7 6AA, + 44 1908 332 92, [email protected]
2
Chalmers University of Technology, Department of Applied Physics, Fysikgränd, 3, F5127 SE-412 96
3
Göteborg, Sweden, Laboratoire Physique des Interactions Ioniques et Moléculaires, UMR 633,
4
Université de Provence CNRS, Centre St-Jérôme, 13397 Marseille Cedex 20, France, Science and
Technology Facilities Council, Rutherford Appleton Laboratory, Harwell, Oxford, Didcot, OX11 0QX, UK,
5
Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A – 6020 Innsbruck, Austria
The precise structure of interstellar ices, Amorphous Solid Water (ASW) in particular, has long
been debated, most importantly the issue of ice porosity1. If interstellar ice is porous this would
inextricably link icy mantles with the earliest stages of planet building through grain aggregation2
and produce grain-surface areas up to three orders of magnitude greater than those currently
utilised in gas-grain chemical models e.g.3. Porosity also greatly enhances the ability of the ice
to uptake, then release (on heating) small gas adsorbates such as N2 CH4 or CO4. This property
provides the strongest evidence that interstellar ices must be porous, accounting for the
differences between predicted and observed gas-phase abundances e.g.5,6. Conversely, no
dangling OH bond features have been reported in ice observations7, and a number of
experiments conclude that interstellar ices must be non-porous, given that the ‘porosity
measurables’, i.e. dangling OH bonds e.g.8, ice height9, and gas ad / desorption rates e.g.10, are
all rapidly diminished as porous ASW is heated, exposed to electron, UV, or ion bombardment
e.g.11,12, or subject to chemical reactions, especially H + H →H213 and H + OH →H2O14,15. Using
the AKARI satellite we have been able to detect the complete interstellar water ice stretching
vibration16, including the dangling-OH bond region. From observations of water ice on hundreds
of lines of sight, we will show upper-limit detections of dangling OH spectra towards a handful of
sources, proving that interstellar ices could have dangling OH bonds. However are the presence
of dangling OH features and gas uptake reliable experimental measures of ice porosity? Recent
neutron scattering data show that even compact ASW ices actually contain pseudo cylindrical
pores of around 10 Å diameter17. We will show that the pore collapse process can only be
initiated by energy input and is not autocatalytic18; such effects can be reproduced by molecular
dynamics simulations of ASW ice-heating19. We can reconcile these new results with previous
interpretations of TPD and RAIRS data, to understand ice porosity under interstellar conditions,
and the effects of this on grain surface reactivity, ice growth20, and ice aggregation21-22. Looking
forwards, this study highlights the need to move beyond “traditional” TPD and RAIRS surface
science techniques to study solid-state ices of astronomical interest. I will finish this presentation
by highlighting some new avenues of research being pursued in the Open University
astrochemistry group, and new activities to more closely link the Physical Chemistry and
Astronomy communities across Europe through the EU COST action CM1401 “Our
Astrochemical History”.
1. Bartels-Rausch et al Rev Mod Phys (2012) 84 885 2.Wang et al ApJ (2005) 620 1027 3. Cazaux et al A&A (2010) 522 A74 4.
Collings et al (2004) MNRAS 354 1123 5. Viti et al MNRAS (2004) 354 1141 6. Brinch et al A&A (2008) 489 617 7.Fraser et al
MNRAS 353 59 (2004) 8. McCoustra & Williams MNRAS (1996) 279 L53 9. Bossa et al A&A (2012) 545 A82 10. May et al J Chem
Phys (2013) 138 104501 11. Palumbo A&A (2006) 453 903 12. Raut et al J Chem Phys (2007) 126 244511 13. Accolla et al PCCP
(2011) 13 8037 14. Oba et al ApJ (2009) 701 464 15. Accolla et al MNRAS (2013) 429 3200 16. Noble et al ApJ (2013) 775 85 17.
Mitteldorfer et al PCCP 16 16013 (2014) 18. Collings et al AP&SS (2003) 285 633 19. Elkind et al JCP (2015) submitted 20. Pascal
et al Nanotech (in prep) 21. Hill et al A&A (2015) 573 49 22. Hill et al A&A (2015) in press
Photoabsorption, Photodissociation, and Photodesorption of Astrophysical Ices
G. M. Muñoz Caro1, R. Martín-Doménech1, J. Manzano Santamaría1, G. A. Cruz
Diaz1, Y.-J. Chen2
1
2
Centro de Astrobiología, INTA-CSIC, Torrejón de Ardoz, 28850 Madrid, Spain
Department of Physics, National Central University, Jhongli City, Taoyuan County
32054, Taiwan
The photodesorption of molecules, induced by VUV irradiation of interstellar and
circumstellar ice analogs in the laboratory, has provided a plausible desorption
mechanism in cold regions where thermal desorption is inhibited. The case of pure
CO ice has been extensively studied because CO ice is not efficiently dissociated at
photon energies below 11 eV, and therefore photodesorption becomes important. In
addition, CO ice has a clear infrared absorption band that allows monitoring of the
photodesorption. But most molecules present in ice mantles are, either efficiently
photodissociated, or not active in the infrared. The study of photodesorption is
therefore more challenging, and the detection of the desorbed molecules and their
photoproducts is made directly in the gas phase. We use IR spectroscopy in
transmittance of the ice and QMS of the desorbed molecules to provide a
quantification of these processes. In addition, the VUV-photoabsorption of the
molecular ice components is also measured, allowing the determination of their
absorption cross sections. The final outcome is the estimation of the photodesorption
rates as the number of photodesorbed molecules per absorbed photon in the ice. Our
recent experimental results will be presented.
Photon Induced Desorption of interstellar relevant ices in the VUV
J.-H. Fillion(1,2), E.C. Fayolle(3), X. Michaut(1), L. Philippe(1), K. Öberg(3), H.
Linnartz(4), C. Romanzin(5) and M. Bertin(1)
(1) Sorbonne Universités, UPMC Univ Paris 06, UMR 8112, LERMA, F-75005, Paris, France
(2) LERMA, Observatoire de Paris, PSL Research University, CNRS, UMR 8112, F-75014, Paris, France
(3) Harvard-Smithsonian Center For Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
(4) Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300
RA Leiden, The Netherlands.
(5) Laboratoire de Chimie Physique, CNRS UMR 8000, Univ Paris Sud, F-91400 Orsay, France.
ABSTRACT
During the cold and dense phase of star- and planet-formation, ices frozen out on microscopic interstellar dust
particles, are the dominant reservoir of molecules other than H 2. When exposed to UV radiation from protostars,
background stars or through secondary H2 emission induced by cosmic rays, the mantle molecules non-thermally
desorb into the gas phase. Because of negligible thermal evaporation in these cold regions, this process is crucial to
explain the abundance of gas phase species below their accretion temperatures.
Previous estimates of the photodesorption rates have been largely based on broadband discharge lamps, peaking at
Ly-α wavelength (10.2 eV), which limits both the understanding of the desorption mechanisms and the applicability
to various astrophysical environments where UV field spectral profiles can be very different. In recent years, we
have developed a novel approach based on the coupling of the “Surface Processes and ICES” set-up to the DESIRS
beamline at SOLEIL, enabling tunable monochromatic excitation of interstellar ice analogs at low temperature (10
K). Instead of probing the depletion of the solid-state molecular concentration to obtain an average desorption rate,
the high photon fluxes provided by DESIRS has opened the opportunity to measure the wavelength dependency of
absolute desorption rates for individual particles ejected into the gas phase. This approach has led to revisit the
desorption mechanisms in the context of astrophysical media.
In this talk, previous results obtained on amorphous ice films of various composition (pure, and binary ices) and
various structures (mixed, layered) will be reviewed. The case of pure CO2 ices will be discussed considering the
chemical composition evolution of ice samples during the irradiation in conditions of laboratory experiments. The
role of indirect desorption induced by CO for the desorption of other organic compounds will be emphasis.
REFERENCES
1. M. P. Brown and K. Austin, The New Physique, Publisher City: Publisher Name, 2005, pp. 25-30.
2. M. P. Brown and K. Austin, Appl. Phys. Letters 85, 2503-2504 (2004).
1. E.C. Fayolle, M. Bertin, C. Romanzin, X. Michaut, K.I. Öberg, H. Linnartz, J.-H. Fillion, Astrophys. J. 739, L36 (2011)
2. M. Bertin, E.C. Fayolle C. Romanzin, , K.I. Öberg X. Michaut, A. Moudens, L. Philippe, P. Jeseck, H. Linnartz, J.-H. Fillion, Phys. Chem.
Chem. Phys. 14, 9929 (2012)
3. E.C. Fayolle, M. Bertin, C. Romanzin, H.A.M. Poderoso, L. Philippe, X. Michaut, P. Jeseck, H. Linnartz, K.I. Öberg, J.-H. Fillion, Astron.
Astrophys. 556, A122 (2013)
4. M. Bertin, E.C. Fayolle, C. Romanzin, H.A.M. Poderoso, X. Michaut, L. Philippe, P. Jeseck, K.I. Öberg, H. Linnartz & J.-H. Fillion,
Astrophys. J. under review (2013)
5. J.-H. Fillion, E.C. Fayolle, X. Michaut, M. Doronin, L. Philippe, J. Rakovsky, C. Romazin, N. Champion, K.I. Öberg, H. Linnartz and M.
Bertin, Faraday Discussions 168, 533 (2014)
THE ROLE OF GROUND STATE N(4S) NITROGEN ATOMS IN THE INTERSTELLAR
DUST GRAINS CHEMISTRY
Lahouari Krim
MONARIS , UMR 8233 du CNRS, de la MOlécule aux NAno-objets : Réactivité, Interactions et
Spectroscopies, Sorbonne Universités, Université Pierre et Marie Curie, UPMC Univ Paris 06, 4
place Jussieu, 75252 Paris cedex 05 France.
Fax 33 (0) 44 27 30 21 / Tel 33 (0)1 44 27 30 23 / Email: [email protected]
Since the detection of the first chemical species in the interstellar media, it was found that a
complex chemistry takes place in this dilute and very cold medium. Using near IR spectroscopy, (a
region which is accessible to ground-based observations) laboratory experiments at very low
temperature and very low pressure under non-energetic conditions are of primary importance to
help understanding processes that may take place in some interstellar regions such as dense clouds.
Although the solid phase experiments are relevant from an astrochemical point of view, one is
unable to characterize all the byproducts formed for a studied reaction, due to the broad absorption
bands of the reactant ices. For this reason, some groups combine two complementary spectroscopy
methods to carry out their studies: infrared and mass spectroscopies. However the mass spectral
results, by warming the solid sample at relatively higher temperature, may be inappropriate to
characterize some reactions that should occur with no additional energy. This is the raison why we
have developed an original experimental approach that combine the study of heterogeneous
reactions (by exposing neutral molecules adsorbed on ice to non-energetic radicals H, OH, N...) and
a neon matrix isolation study at very low temperatures, which is of paramount importance to isolate
and characterize highly reactive reaction intermediates. Such experimental approach has already
provided answers1-4 to many questions raised about some astrochemically-relevant reactions
occurring in the ground state on the surface of dust grain ices in dense molecular clouds. The aim of
this new present work is to show the implication of ground state atomic nitrogen on hydrogen atom
abstraction reactions from some astrochemically-relevant species, at very low temperatures (3K20K), with no additional energy. Under cryogenic temperatures and with high barrier heights, such
reactions involving N(4S) nitrogen atoms should not occur spontaneously and require an initiating
energy. However, the detection of some radicals species as byproducts, in our solid samples left in
the dark for hours at 10K, proves that hydrogen abstraction reactions involving ground state N(4S)
nitrogen atoms may occur in solid phase at cryogenic temperatures. Our results show the efficiency
of radical species formation stemming from non-energetic N-atoms and astrochemically-relevant
molecules such as CH4, CH3OH and NH3. Such reactions, involving nitrogen atoms in their ground
states, may occur on the surface of dust grain ices in dense molecular clouds, could be the first key
step towards complex organic molecules production in the interstellar medium, and should be taken
into account in the astrochemical models.
Refrences
(1) C. Pirim, L. Krim. Phys. Chem. Chem. Phys. 13, 19454 (2011), (2) P. Joshi, E. Zins, L. Krim Mon. Not. Roy. Astron. Soc. 419,
1713 (2012). (3) E. Zins, L. Krim RSC Advances. 4, 22172, (2014), (4) C. Pirim, L. Krim RSC Advances. 4, 15419, (2014).
Chemistry of ammonia ices under irradiation of energetic electrons
Marko Förstel, Pavlo Maksyutenko, Brant M. Jones and Ralf I. Kaiser
Department of Chemistry
W. M. Keck Research Laboratory in Astrochemistry
University of Hawaii at Manoa, Honolulu, Hawaii, HI, 96822, USA
Ammonia and/or ammonia hydride has been found in many places in our solar system; the atmospheres of
Jupiter, Saturn, Uranus and Neptune, on Kuiper belt objects and on comets[1-6]. Together with water,
carbon monoxide, carbon dioxide, methane and others, these solar system bodies possess a rich and
complex chemical environment which is constantly subject to ionizing radiation. We are aiming to fathom
the radiation induced chemistry in these systems and the study of their constituents is a necessary starting
point for the understanding of their multifaceted, heterogeneous chemistry.
Figure 1: Selected time programmed desorption profiles of ions detected in a time of flight mass spectrometer using soft x-ray
ionization at 10.5eV. Shown in blue are the traces of ice irradiated with 5keV electrons and in red the traces of the unirradiated
ice.
In this talk I report new experimental findings complimenting and extending an earlier infrared
absorption study on ammonia ice exposed to ionizing radiation[7]. Briefly, pure ammonia ice was
bombarded with 5keV electrons and the newly formed reaction products were then identified using
temperature program desorption coupled with soft photoionization reflectron time of flight mass
spectroscopy. With this very sensitive method we could not only clarify and confirm earlier tentative
assignments of molecules formed in the ice but also detect a new molecule - triazene. Triazene is a
potential high energy molecule which has not been isolated before[8].
References:
[1]
S.K. Atreya, P.R. Mahaffy, H.B. Niemann, M.H. Wong, T.C. Owen, Planetary and Space Science 51
(2003) 105.
[2]
J.M. Bauer, T.L. Roush, T.R. Geballe, K.J. Meech, T.C. Owen, W.D. Vacca, J.T. Rayner, K.T.C. Jim,
Icarus 158 (2002) 178.
[3]
J.M. Greenberg, C.E.P.M. Van de Bult, L.J. Allamandola, The Journal of Physical Chemistry 87
(1983) 4243.
[4]
M.D. Hofstadter, D.O. Muhleman, Icarus 81 (1989) 396.
[5]
G.F. Lindal, Astronomical Journal 103 (1992) 967.
[6]
S. Maret, E.A. Bergin, C.J. Lada, Nature 442 (2006) 425.
[7]
W. Zheng, D. Jewitt, Y. Osamura, R.I. Kaiser, The Astrophysical Journal 674 (2008) 1242.
[8]
R.M. Richard, D.W. Ball, Journal of molecular modeling 14 (2008) 29.
1
The Role of Low-Energy (< 20 eV) Electrons in Astrochemistry
Katherine D Tran, Sebiha M Abdullahi, and Chris Arumainayagam
Wellesley College,
Wellesley, MA 02481
In the interstellar medium, UV photolysis of ice mantles encasing dust grains is thought to be the
mechanism that drives the synthesis of “complex” molecules. The source of this reactioninitiating UV light is assumed to be local because externally sourced UV radiation cannot
penetrate the ice-containing dark, dense molecular clouds. Specifically, high-energy cosmic rays
penetrate and ionize the molecular clouds, generating secondary electrons. Hydrogen molecules,
present within these dense molecular clouds, are excited in collisions with these secondary
electrons. The UV light emitted by these electronically excited hydrogen molecules is generally
thought to photoprocess interstellar ice mantles to generate “complex” molecules. In addition to
producing UV light, the large numbers of low-energy (< 20 eV) secondary electrons, produced
by cosmic rays, can also directly initiate radiolysis reactions in the condensed phase. We
hypothesize that cosmic-ray induced low-energy electron processing of interstellar ices may
occur via three mechanisms:(1) the interaction of cosmic rays with gaseous molecular hydrogen
producing low-energy electrons that can interact with the surface (top few molecular layers) of
cosmic ices, (2) the interaction of cosmic rays with molecules within cosmic ices generating a
cascade of low-energy electrons that can interact with the surface and the bulk of the ice mantles,
(3) the interactions of the cosmic rays with the dust grain beneath the ice mantle engendering
low-energy electrons that can interact with the bottom ice layers in contact with the dust grain.
The goal of our studies is to understand the low-energy, electron-induced processes that occur
when high-energy cosmic rays interact with interstellar ices. Using post-irradiation temperatureprogrammed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS), we have
investigated the radiolysis initiated by low-energy (5 – 20 eV) electrons in condensed methanol,
ammonia, and water at ~ 90 K under ultrahigh vacuum (1×10−9 Torr) conditions. Our
experimental results suggest that low-energy, electron-induced condensed phase reactions may
contribute to the interstellar synthesis of “complex” molecules previously thought to form
exclusively via UV photons.
Detection of Large Complex Organics via Reflectron Time-of-Flight Mass Spectroscopic
Analysis of Methanol and Methanol:Carbon Monoxide Ices Exposed to Ionizing Radiation
Brant M. Jones, Surajit Maity, and Ralf Kaiser
University of Hawaii at Manoa
Department of Chemistry,
W.M. Keck Research Laboratory in Astrochemisty,
Honolulu, HI 96822
I will present recent results regarding the formation of complex organics starting from simple
methanol and mixed methanol – carbon monoxide ices upon interaction of these ice systems with
ionizing radiation. Specifically, we have utilized reflection time-of-flight mass spectrometry
(ReTOF) coupled with soft vacuum ultraviolet photoionization to observe high mass, complex
organics as a function of their respective sublimation temperature.
Surfaces of interstellar dust grains are enclosed with an icy shell consisting of simple carbon,
hydrogen, oxygen, and nitrogen containing molecules. These micron sized dust grains have
undergone millions of years of chemical processing due to ionizing radiation from galactic
cosmic radiation and Lyman α photons from the interstellar UV field. Laboratory experiments
have unequivocally shown that energetic processing of frozen gases by ionizing radiation will
produce complex organics. These organics may then sublime for instance, via photodesorption,
grain – grain collisions, shocking of the interstellar medium and/or direct thermal sublimation via
hot cores. Our research has been focused on trying to understand how these ices have chemically
and physically evolve by simulating the processing in an ultrahigh vacuum chamber coupled
with in situ FTIR spectroscopy along with gas phase mass spectroscopy. Despite, numerous
previous experimental investigations examining the effect of ionizing radiation on simple
astrophysical ice analogues, our results suggest that there is still a vast unknown collection of
molecules formed upon exposure of these ices to ionizing radiation. For example, recent results
of the products synthesized from the energetic processing of simple amorphous methanol and
methanol:carbon monoxide mixed ice systems indicate the possible formation of sugars with up
to a five carbon chain backbone.
CONTRIBUTION OF QUANTUM CHEMICAL METHODS IN THE STUDY OF ICEBASED COSMOCHEMISTRY
Albert Rimola
Departament de Química, Universitat Autònoma de Barcelona, 08193, Bellaterra, Catalonia,
Spain
0034 93 5812173 / [email protected]
ABSTRACT
The existence of cosmic molecules is of great relevance due to their connection with the
chemical evolution steps occurring in the universe [1,2]. A key role of this chemical evolution is
played by reactions occurring on or in cosmic ices. The current knowledge of the chemistry
derived from these ices is mostly based on spectroscopic observations, helped by laboratory
experiments and astrochemical models. This combination has been fruitful to obtain important
information, such as the chemical activity of an ice with a given composition [3]. However, this
approach cannot provide atomic-scale information such as the precise mechanistic steps and
quantitative energetic data of the reactions, or the exact role played by the icy particles. This is a
serious limitation to fully understand the basic physical and chemical steps that lead to the
chemical complexity in space. This information gap, however, can partly be filled in by using
theoretical calculations based on quantum mechanical approaches [4]. In this presentation,
examples on how these theoretical calculations can contribute to ice-based cosmochemical
studies in both rationalizing puzzling experimental results as well as predicting possible reaction
channels will be presented. In particular, results obtained from simulations devoted to the
formation of H2CO and CH3OH, both through H additions to CO on water ice nanoparticles and
in the presence of an extra electron embedded in the water ice, will be shown [5]. Finally, the
fruitful interplay between theory and experiment will be demonstrated showing results focused
on the formation of formaldehyde derivatives in water-dominated cometary ices [6,7].
REFERENCES
[1] A.G.G.M. Tielens, Rev. Mod. Phys., 2013, 85, 1021.
[2] P. Caselli, C. Ceccarelli, A&AR, 2012, 20, 1.
[3] T. Hama & N. Watanabe, , Chem. Rev., 2013, 113, 8783.
[4] S.T. Bromley, T.P.M. Goumans, E. Herbst, A.P. Jones & B. Slater, Phys. Chem. Chem.
Phys., 2014, 16, 18623.
[5] A. Rimola, V. Taquet, P. Ugliengo, N. Balucani & C. Ceccarelli, submitted to A&A.
[6] G. Danger, A. Rimola, N.A. Mrad, F. Duvernay, G. Roussin, P. Theule, T. Chiavassa, Phys.
Chem. Chem. Phys., 2014, 16, 3360.
[7] F. Duvernay, G. Danger, P. Theule, T. Chiavassa, A. Rimola, ApJ, 2014, 791, 75.
Poster Presentations
Monday, February 23, 8:25 to 10:05 p.m.
P. Brandon Carroll
THz Spectroscopy of PAHs
Sebiha M Abdullahi
Revisiting Water Radiolysis
Jiao He
Formation of Hydroxyl amine on Dust Grains via
Ammonia Oxidation
Antonio Jimenez-Escobar
X-ray Irradiation of realistic H2O:CO ice mixtures.
Yuki Kimura
Molecular Formation Experiment by Catalytic
Reaction on Inorganic Surfaces at Low Pressure
Environment
Léon Sanche
Cyanide and old Ice: Radiation Induced C-N Bond
Coupling in Simulated Interstellar CO2/NH3 Ices
Niels Ligterink
Search for methylamine in high mass hot cores
Kazuya Osaka
Water Formation by Reaction of Solid Hydrogen
Peroxide with Hydrogen Atoms at Low
Temperatures via Quantum Tunneling
Sergio Ioppolo
THz and Mid-IR Spectroscopy of Interstellar CO2
and CH3OH Ice
Christopher N. Shingledecker
Cosmic Ray Induced Interstellar Grain Chemistry:
A “Big-Data” Approach
Tetsuya Hama
Controlling Hydrogenation of Solid Benzene by
Quantum Tunneling via Surface Structure
THz Spectroscopy of PAHs
P. Brandon Carroll, Marco A. Allodi, Sergio Ioppolo, Brett A. McGuire, & Geoffrey A. Blake
1200 E. California Blvd, Pasadena CA, 91125
(626) 395-6824/[email protected]
Polycyclic aromatic hydrocarbons (PAHs) present themselves as a strong candidate as carriers of the unidentified infrared
features (UIRs). As UIR carriers, PAHs may account for up to 20% of the interstellar carbon budget and may play key roles in
many chemical and physical processes in the ISM, and yet our inability to definitively detect PAHs hinders our ability to evaluate
the role they may play. A possible solution is observations in the TeraHertz (THz) regime, where observed transitions are specific
to each molecule. Recent advances in THz technology have enabled both laboratory spectroscopy and astronomical observations
in this region. A first step in both laboratory and astronomical studies of PAHs is the acquisition of spectra of pure PAH samples.
Here, we present the THz time-domain spectra (0.3 - 7 THz) of several PAHs, including naphthalene, anthracene, and pyrene,
and discuss the utility of these spectra for future laboratory and astronomical studies.
s
Revisiting Water Radiolysis
Sebiha M Abdullahi, Katherine D Tran, and Chris Arumainayagam
Wellesley College,
Wellesley, MA 02481
The goal of our research is to obtain a fundamental understanding of water radiolysis, an
important topic that has been studied extensively since the discovery of natural radioactivity in 1896.
Radiolysis of “dirty” water ice in the interstellar medium could have led to the synthesis of
“complex” organic molecules which could be precursors for prebiotic molecules. To study the
radiolysis of water, nanoscale-thin films of solid amorphous water are deposited on a Mo(110) single
crystal substrate at 90 K in an ultrahigh vacuum (UHV) chamber. An electron gun is used to irradiate
the thin films with low- and high- energy electrons ranging from ~5 to 1000 eV. Post-irradiation
analysis of the species left behind in the film is done with temperature-programmed desorption
(TPD) and infrared reflection absorption spectroscopy (IRAS). Because copious amounts of lowenergy (< 20 eV) secondary electrons are produced when high-energy radiation interacts with
condensed matter, our goal is to verify the hypothesis that it is these low-energy electrons that
mediate high-energy condensed-phase water radiolysis.
Formation of Hydroxylamine on Dust Grains via Ammonia
Oxidation
Jiao He1* , Gianfranco Vidali1 , Jean-Louis Lemaire2 , and Robin T. Garrod3
1
Physics Department, Syracuse University, Syracuse, NY 13244
Current Address: Department of Chemistry, University of Hawaii at Manoa, Honolulu,
HI 968222 Email: [email protected]
2
Paris Observatory, Paris, France
3
Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA
*
Hydroxylamine is considered to be a precursor to the formation of glycine, which is
an important prebiotic molecule. Although not yet detected in the interstellar medium,
the detection of hydroxylamine is likely with ALMA. Because of the ubiquity of NH3 and
atomic oxygen in molecular clouds, the formation of hydroxylamine via ammonia oxidation
seems plausible. We performed temperature programmed desorption (TPD) experiments
to study the formation of hydroxylamine. Ammonia and atomic oxygen were sequentially
deposited onto an amorphous silicate surface when the surface was kept at 70 K. In the subsequent TPD, hydroxylamine (m/z=33) and its fragments were detected using a quadrupole
mass spectrometer (QMS). Control experiments confirmed that hydroxylamine is formed
by NH3+O instead of NH3 +O2 or NH3 +O3 . The reaction efficiency was quantized by the
destruction rate of ammonia exposed to different doses of atomic oxygen, and the reaction NH3 +O→NH2 OH was found to be efficient. A simulation using a three phase dense
cloud model supports that the ammonia oxidation is an important formation mechanism for
hydroxylamine.
This work is supported by the NSF Astronomy and Astrophysics Division (Grant No.1311958 to GV). We thank
Dr. J. Brucato of the Astrophysical Observatory of Arcetri (Italy) for providing the sample used in these experiments
and Zhirou Zhang, Jianming Shi, and Tyler Hopkins for technical help. RTG acknowledges the support of the NASA
Astrophysics Theory Program (Grant No. NNX11AC38G).
REFERENCE
He, J., Vidali, G., Lemaire, J.L., and Garrod, R., ApJ accepted (2014)
X-ray Irradiation of realistic H2O:CO ice mixtures.
A. Jimenez-Escobar1, A. Ciaravella1, Y.-J. Chen2, C. Cecchi-Pestellini1,G. M. Muñoz-Caro3
1 INAf-Osservatorio Astronomico di Palermo, Palermo, Italy
2 Department of Physics, National Central University, Jhongli City, Taiwan
3 Centro de Astrobiología (INTA-CSIC),Torrejón de Ardoz, Spain
[email protected], [email protected],
[email protected], [email protected],
[email protected]
ABSTRACT
H2O:CO ice mixtures were irradiated at 14 K with monochromatic soft X-rays of 300, 550, and
900eV and with a broad spectrum (250 - 1200 eV). During irradiation, new products of
astrophysical interest were identified through its new infrared absorption bands such as CO 2,
HCO, H2CO, HCOOH, CH3OH. Carbon suboxides including C 3O2, C3, C2O, and CO3 have
been detected solely after irradiation with broad spectrum. During the subsequent warm-up of the
irradiated samples, the infrared features of H2CO3 and O3 were detected. Monochromatic
experiment with 550 eV photons shows a larger H2O destruction, at the same absorbed Energy,
displaying the role of the photon energy. The chemical network of the new species will be
discussed.
REFERENCES
MOLECULAR FORMATION EXPERIMENT BY CATALYTIC REACTION ON
INORGANIC SURFACES AT LOW PRESSURE ENVIRONMENT
Yuki Kimura1, Naoki Watanabe1, Akira Tsuchiyama2, Hiroko Nagahara3, Akira Kouchi1
1
Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060–0819,
Japan
2
Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University
3
Department of Earth and Planetary Science, Graduate School of Science, The University of
Tokyo
[email protected]
ABSTRACT
At the transit stage from molecular cloud to primitive solar nebula, more complex
molecules were produced from abundant H2, CO and N2 gases reacted mainly on the cooled
surface of cosmic dust particles [1]. The complex molecules might be incorporated into the
primordial organic system of the Earth and have some contribution on the evolution of life.
Nanometer sized cosmic dust particles may work as catalysts to produce organic materials in the
solar nebula after the formation of simple molecules in the molecular cloud. In the previous
experimental study, organic molecules ranging from methane (CH4), ethane (C2H6), benzene
(C6H6) and toluene (C7H8), to more complex species such as acetone (C3H6O), methyl amine
(CH3NH2), acetonitrile (CH3CN) and N-methyl methylene imine (H3CNCH2) have been
produced using such as the Fischer-Tropsch type (FTT) and Haber-Bosch type (HBT) reactions
on analogs of naturally occurring grain surfaces at higher-temperature (>573 K) and pressure (~1
atm) than the expected conditions in the solar nebula [2-6]. In this project, we have performed
molecular formation experiments in a more plausible environment [lower temperature (100-500
K) and pressure (10-3-100 Pa)].
We are constructing a vacuum chamber based on a new concept to conduct the experiments
mentioned above. The chamber with a differential pumping system has a temperature-controlled
substrate, a Fourier transform infrared spectrometer (FT-IR), and two quadrupole mass
spectrometers (Q-MSs). FT-IR measures the vibration modes of adsorbed and produced
molecules on the surface and the Q-MSs detect volatile molecules, respectively. As a
preliminary experiment, the substrate has a gold thin film was used in a continuous gas flow of a
mixture gas of H2 and CO for FTT reactions to check the background. Then, the gold thin film is
replaced by magnesium silicate thin film. Resulting reaction rates of molecules on the substrates
will be shown as a function of temperature and pressure in the workshop.
REFERENCES
[1] J. Llorca and I. Casanova, Meteorit. Planet. Sci. 35, 841 (2000).
[2] H. G. G. M. Hill, and J. A. Nuth, Astrobiology 3, 291 (2003).
[3] J. A. Nuth, N. M. Johnson, and S. Manning, The Astrophysical Journal 673, L225 (2008).
[4] J. A. Nuth, N. M. Johnson, and S. Manning, Organic matter in space, Proc. IAU Symp. 251,
edited by S. Kwok and S. Sandford, Cambridge Univ. Press, NY (2008), pp. 403–408.
[5] J. A. Nuth, Y. Kimura, C. Lucas, F. Ferguson, and N. M. Johnson, The Astrophysical Journal
Letters 710, 98 (2010).
[6] Y. Kimura, J. A. Nuth, N. M. Johnson, K. D. Farmer, K. P. Roberts, and S. R. Hussaini,
Nanoscience and Nanotechnology Letters 3, 4 (2011)
Cyanide and old ice: radiation induced C-N bond coupling in simulated interstellar CO2/NH3 ices
S. Esmaili, A.D. Bass, P. Cloutier, L. Sanche, and M. A. Huels
Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences,
University of Sherbrooke, Sherbrooke, QC, Canada J1H 5N4
More than 180 molecules, many of them organic or biotic, have been observed within interstellar
media (ISM). Experimental and observational evidence supports the notion that much of this
intriguing molecular diversity arises from heterogeneous chemistry occurring on icy surfaces of
ISM dust grains [1]. These ices are exposed to ionizing radiation including UV, x-ray and cosmic
radiation fields, and secondary electrons with initial energies less than 100 eV are abundantly
produced along ionizing radiation tracks. Thus, one approach to investigate the chemistry
occurring in these ices is to irradiate nanometer thick molecular solids of simple molecular
constituents, with energy selected electron beams, and to monitor the electron stimulated
desorption of new molecular product ions [2]. Of particular interest is the formation of HCN,
which is a tracer of dense gases in interstellar clouds, and is ubiquitous in the ISM. Moreover, the
study of the formation and subsequent radiation chemistry of HCN fragments such as CN- is
essential to the understanding of the basic building blocks of life such as amino acids [3, 4] or
purine bases of DNA, e.g. adenine, which consist essentially of HCN subunits. Here we present
measurements of 70 eV electron irradiation of multilayer films of CO2, NH3 and CO2/NH3
mixtures (1:1) on Pt(111). The electron stimulated desorption (ESD) yields of cations and anions
are recorded as a function of electron fluence. Measurements at very low fluence show the
prompt desorption of cationic reaction/scattering products, e.g. C2+,C2O2+, C2O+, CO3+, C2O3+ or
CO4+ from pure CO2, and NH4+, N2+, N2H+ from pure NH3, and NO+, NOH+ from CO2/NH3
mixtures. Most saliently, increasing signals of negative ion products desorbing during prolonged
irradiation of CO2/NH3 films included C2, C2H, C2H2, as well as CN, HCN and H2CN. The
gradual appearance of the desorption signals of the latter three anions during continuing
irradiation, suggests that these fragments result from the dissociation of much larger molecules
that contain new nitrile groups, and which form during electron irradiation of these simulated
interstellar surface ices. In our experiments, the identification of particular product ions was
accomplished by using 13CO2 and 15NH3 isotopes (This work has been funded by NSERC).
REFERENCES
[1] N. J. Mason, A. Dawes, P. D. Holtom, R. J. Mukerji, M. P. Davis, B. Sivaraman, R. I. Kaiser,
S. V. Hoffmann, and D. A. Shaw, Faraday Discuss. 133, 311 (2006).
[2] M. A. Huels, L. Parenteau, A. D. Bass, and L. Sanche, International Journal of Mass
Spectrometry 277, 256 (2008).
[3] M. H. Vera, Y. Kalugina, O. Denis-Alpizar, T. Stoecklin, and F. Lique, J. Chem.
Phys. 140 (2014).
[4] J. Loison, V. Wakelam, and K. M. Hickson, Monthly Notices of the Royal Astronomical
Society 443, 398 (2014).
Search for methylamine in high mass hot cores Niels Ligterink1,2, Ewine van Dishoeck1,3 1
Leiden Observatory, Leiden University, 2Raymond and Beverly Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University, 3Max­Planck Institut für Extraterrestrische Physik (MPE), Garching Methylamine is potentially an important tracer for the importance of UV radiation in inducing chemistry in ice mantles on interstellar dust grains. The formation of methylamine is thought to follow from the addition of the CH3 and NH2 radical [Garrod et al. 2008], which in turn are formed by UV photodissociation of methane and ammonia. Subsequent heating of the ice mantles as the dust grains move inwards to the protostar causes the radicals to become mobile and react with each other. Further heating results in the release of the newly formed methylamine to the gas phase, from where its rotational spectrum can be detected by telescopes on Earth and in space. A particularly interesting molecule to compare with methylamine is formamide, NH2CHO. Whereas methylamine has so far only been detected toward the galactic center [Belloche et al. 2013 e.g.], formamide is more widely observed [Halfen et al. 2011, Bisschop et al. 2007 e.g.] and is in fact the most observed amine containing molecule. Contrary to the proposed radical­radical interaction that forms methylamine, formamide can be formed by H and N atom addition to CO or H atom addition to HNCO (isocyanic acid). In this poster deep JCMT searches for a number of methylamine transitions toward nine high mass hot cores are presented [Ligterink et al. submitted]. This did not result in clear methylamine detections, however it was possible to determine upper limits of CH3NH2. Comparisons are made with results from Bisschop et al. 2007 and Isokoski et al. 2013, whose data were taken towards the same sources using the same telescope making a direct comparison possible. Abundance ratios of methylamine over formamide, methanol and acetonitril are obtained and compared with model values of Garrod et al. 2008, which show that methylamine is overproduced in these models. Further conclusions are drawn about methylamines origin, its potential as UV tracer and the nitrogen chemistry in the studied hot cores. R.T. Garrod, S.L. Widicus Weaver, E. Herbst, 2008, APJ 682:283­302 A. Belloche, H.S.P. Müller, K.M. Menten et al. 2013, A&A 559, A47 D. T. Halfen, V. Ilyushin and L. M. Ziurys, 2011, APJ 743:60 S.E. Bisschop, J. K. Jørgensen, E. F. van Dishoeck et al. 2007, A&A 465, 913­929 N.F.W. Ligterink, E.D. Tenenbaum and E.F. van Dishoeck, A&A, submitted K. Isokoski, S. Bottinelli, E.F. van Dishoeck, 2013, A&A 554, A100 Contact or more information: [email protected] Water Formation by Reaction of Solid Hydrogen Peroxide with Hydrogen Atoms at Low
Temperatures via Quantum Tunneling
K. Osaka1, Y. Oba1, A. Kouchi1, and N. Watanabe1
1Institute of Low Temperature Science, Hokkaido University, Japan
+81-11-706-5477/[email protected]
ABSTRACT
Water (H2O) is one of the most important constituents of icy grain mantles in molecular clouds.
The observed abundance of water molecules cannot be explained only by the gas phase synthesis,
and thus surface reactions on cold interstellar grains must play an important role. H2O formation
has been proposed to originate from hydrogenation of atomic oxygen (O), molecular oxygen (O2),
or ozone (O3), and is completed by the following reactions [1,2]:
OH + H → H2O,
(1)
OH + H2 → H2O + H,
(2)
H2O2 + H → H2O + OH.
(3)
Among these reactions, the experimental study of reaction (3) is associated with difficulty in
producing pure solid H2O2 and therefore has remained to be done. Here we report experimental
results on the formation of H2O via reaction (3) and its isotope effect using high-purity (>95%)
solid H2O2 and D2O2.
Experiments were performed using the Apparatus for SUrface Reations in Astrophysics
(ASURA), which mainly consists of a main chamber, and an atomic source chamber. Pure solid
H2O2 (D2O2) was prepared by the codeposition of H atoms with O2 molecules on a substrate at
45-50 K and then exposed to cold H (D) atoms (100 K) at 10-30 K. The reaction products were
measured by FT-IR in situ.
We found that the H2O2 solid reacts with both H and D atoms at 10–30 K despite the large
activation barriers (~2000 K) [3] and also that the rate of reaction with H atoms is approximately
45 times faster than that with D atoms at 15 K. This isotope effect suggests that these reactions
occur through quantum tunneling. We will further discuss the astrophysical implications of this
work in the poster.
REFERENCES
[1]
[2]
[3]
A. Tielens and W. Hagen, Astron. Astrophys., 1982, 114, 245–260
H. M. Cuppen and E. Herbst, Astrophys. J., 2007, 668, 294–309
R. Atkinson et al., Atmos. Chem. Phys., 2004, 4, 1461–1738
THz AND MID-IR SPECTROSCOPY OF INTERSTELLAR CO2 AND CH3OH ICE
S. Ioppolo1, X. de Vries2, B. A. McGuire3, M. A. Allodi3, P. B. Carroll3, G. A. Blake3, 4
1
Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen NL6500 GL, NL
3
Division of Chemistry and Chemical Engineering, Caltech, 1200 E California Blvd., Pasadena, USA
4
Division of Geological and Planetary Science, Caltech, 1200 E California Blvd., Pasadena, USA
2
Fax: +1-(626)-5851917 / Tel: +1-(626)-3956296 / Email: [email protected]
Astrochemistry is currently being driven forward by an impressive amount of high quality
observational data from astronomical facilities in the far-infrared (far-IR), submillimeter, or
terahertz (THz) frequency range. The Herschel archive as well as data from SOFIA and ALMA
provide valuable information on the rotational motions of small molecules, the rovibrational
transitions of larger species, interlayer vibrational and single molecule torsional modes of ices,
and phonon modes in solids. Moreover, due to the long-range nature of the forces involved in the
THz modes of solids, these data potentially contain information on the structure, composition,
and thermal processing history of interstellar dust and ice [1, 2]. Therefore, spectroscopy in the
THz region of the electromagnetic spectrum holds the key to our ability to understand the
physics and chemistry of the interstellar medium. Ices, however, have typically only been
observed under specific conditions via mid-IR absorption spectroscopy toward the line of sight
to bright sources (i.e., field stars or protostars). THz spectroscopy provides the unique
opportunity to detect ices in disks and clouds in either emission or absorption against the dust
continuum, through a number of distinct features and, theoretically, along any line of sight. To
take full advantage of the enormous amount of available observations, laboratory analogs must
be studied systematically. After water ice [3], carbon dioxide (CO2) and methanol (CH3OH) are
the best candidates to be observed at THz frequencies, because of their abundance relative to
water and their clear and distinct THz features in the solid phase [2, 4].
My poster will review the latest laboratory results on THz Time-Domain spectroscopy of
CO2 and CH3OH ices as obtained by the Blake Research Group at Caltech. The THz TD
spectrometer that my co-workers and I have constructed and optimized relies upon an ultrafast
laser system to generate and detect THz pulses in the range between 0.3 - 7.5 THz (10 - 250 cm-1
or 1000 - 40 µm). The system is coupled to a FT-IR spectrometer to monitor the ices in the midIR (4000 - 500 cm-1 or 2.5 - 20 µm). Laboratory results are supported by theoretical calculations
to retrieve fundamental information on the nature of the phonon vibrational modes observed in
our THz spectra.
REFERENCES
[1] Allodi, Ioppolo, Kelley, McGuire, Blake 2014, PCCP, 16, 3442. [2] Ioppolo, McGuire,
Allodi, Blake 2014, FD 168, 461. [3] McClure, Manoj, Calvet, Adame, Espaillat, Watson,
Sargent, Forrest, D’Alessio 2012, ApJL, 759, 10. [4] General Discussion 2014, FD 168, 423.
Cosmic-Ray Induced Interstellar Grain Chemistry: A “Big-Data”
Approach
Christopher N. Shingledecker and Eric Herbst
Department of Chemistry, University of Virginia
Charlottesville, VA 22904
email: [email protected]
Abstract
A lingering problem in the field of astrochemistry is how to treat the interaction between cosmic radiation,
which consists mostly of high-energy protons, and interstellar dust grains. The ices that cover these dust
grains are the engine that drives much of the complex chemistry observed in these regions. Much of the
difficulty in incorporating collisions between cosmic rays and dust grains into existing astrochemical models
is due to the number of possible physical processes that can occur, such as the desorption of energized species
and a cascade of up to 104 secondary electrons produced in collisions between the ion and bulk [4]. These
electrons have energies of less than 50 eV [2] and can, in turn, interact with the surrounding molecules via
a variety of mechanisms, many of which lead to molecular dissociation [1].
Our initial approach to this problem is to extend current methods for simulating grain chemistry by
reducing the complexity of the physics through reasonable approximations. The basis for the grain chemistry
is the kinetic Monte Carlo model described in Chang and Herbst [3]. There, the ice is represented as a three
dimensional matrix comprised of normal crystal lattice sites and interstitial sites which can be thought of as
potential locations for inclusions within the structure. Cosmic-ray collisions are treated stochastically. Their
tracks within the matrix are calculated and interactions can occur when the track crosses an occupied site.
Electrons produced in ionization events are placed at a random, nearby site and react immediately with a
neighboring species. Ionic species thus produced are made to recombine. Finally, in order to overcome the
limits of running this simulation on a single processor, the program will be run on a large multiprocessor
type supercomputer. This will be accomplished by dividing the total grain surface into a large number of
discrete units, each running on one node of a supercomputer.
References
[1] C. R. Arumainayagam, H.-L. Lee, R. B. Nelson, D. R. Haines, and R. P. Gunawardane. Low-energy
electron-induced reactions in condensed matter. Surface Science Reports, 65(1):1–44, Jan. 2010.
[2] E. M. Bringa and R. E. Johnson. A new model for cosmic-ray ion erosion of volatiles from grains in the
interstellar medium. The Astrophysical Journal, 603(1):159, 2004.
[3] Q. Chang and E. Herbst. Interstellar simulations using a unified microscopic-macroscopic monte carlo
model with a full gas-grain network including bulk diffusion in ice mantles. The Astrophysical Journal,
787(2):135, June 2014.
[4] N. J. Mason, B. Nair, S. Jheeta, and E. Szymaska. FD 168: Electron induced chemistry a new frontier
in astrochemistry. Faraday Discussions, 2014.
1
Controlling Hydrogenation of Solid Benzene by Quantum Tunneling via Surface Structure
Tetsuya Hama,† Hirokazu Ueta,† Akira Kouchi,† Naoki Watanabe,† and Hiroto Tachikawa‡
†Institute of Low Temperature Science, Hokkaido University
‡Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University
[email protected]
Polycyclic aromatic hydrocarbons (PAHs) and mixed aromatic/aliphatic carbonaceous dusts are
abundant in the interstellar medium. Benzene (C6H6), the building block of PAHs, has also been
detected in circumstellar environments such as post-asymptotic giant branch objects. C6H6 can
be produced in cold interstellar clouds, typically at 10 K via gas-phase reactions, in which the
calculated abundance was < 10−9 with respect to H2.1 Surface reactions with H atoms are some of
the most important chemical processes for these materials.2 However, activation barriers of about
20 kJ mol-1 exist for hydrogenation of aromatic hydrocarbons in order to break the aromaticity.
Here, we show that H atoms can efficiently add to C6H6 molecules on the surface of amorphous
C6H6 solid at 10–50 K by quantum tunneling to form cyclohexane (C6H12).
C6H6 + H → C6H7, Ea = 18.2 kJ mol−1, (1)
C6H7 + H → C6H8,
(2)
C6H8 + H → C6H9, Ea = 6.3 kJ mol−1,
(3)
C6H9 + H → C6H10,
(4)
−1
C6H10 + H → C6H11, Ea = 10.5 kJ mol , (5)
C6H11 + H → C6H12,
(6)
Ea represents the activation barrier in the gas phase. In situ infrared spectroscopy revealed that
cold H atoms can add to the amorphous C6H6 surface at 10–50 K to form C6H12 by tunneling.
The present study suggests that cyclic alkenes and alkanes, such as C6H10 and C6H12, can be
formed on the surface of dust grains in interstellar clouds following subsequent H atom addition
to aromatic molecules (e.g., C6H6) once the surface temperature reaches at 10–50 K. We also
infer that it can efficiently occur in the outer disk in protoplanetary disks, where the temperature
drops below 50 K.
We also found that the surface structure
strongly controls the hydrogenation
efficiency; hydrogenation is greatly
reduced on crystalline C6H6 (Figure). We
suggest that the origin of the high
selectivity of this reaction is the large
difference in geometric constraints
between the amorphous and the
crystalline surfaces. The present findings
can improve our understanding of
heterogeneous
reaction
systems,
especially those involving tunneling.3
Figure. Schematic illustration of the present study.
REFERENCES
1. Jones et al., PNAS. 2011, 108, 452–457.
2. Skov et al., Faraday Discuss. 2014, 168, 223–234.
3. Hama et al., J. Phys. Chem. Lett. 2014, 5, 3843−3848.
List of Participants
Last Name
First Name
Abdullahi
Abplanalp
Ahmed
Anderson
Boogert
Bossa
Brumer
Carroll
Chen
Cheng
Continetti
Crandall
D'Angelo
Dartois
de Marcellus
Ehrenfreund
Fillion
Förstel
Fraser
Gavilan
Geppert
Gorczyca
Gordon
Gudipati
Sebiha
Matthew
Musahid
David
Adwin
Jean-Baptiste
Paul
Brandon
Yu-Jung
Bing-Ming
Robert
Parker
Martina
Emmanuel
Pierre
Pascale
Jean-Hugues
Marko
Helen
Lisseth
Wolf
Thomas
Karl
Murthy
Hama
Hanstorp
He
Henning
Hornekær
Hudson
Ioppolo
JimenezEscobar
Jones
Kaiser
Tetsuya
Dag
Jiao
Thomas
Liv
Reggie
Sergio
Kimura
Yuki
Antonio
Brant
Ralf
Affiliation
Wellesley College
University of Hawaii at Manoa
Lawrence Berkeley National Laboratory
University of Wyoming
USRA/SOFIA, NASA Ames
Leiden University
University of Toronto
California Institute of Technology
National Central University
National Synchrotron Radiation Research Center
University of California at San Diego
University of Hawaii at Manoa
University of Groningen
Institut d'Astrophysique Spatiale
Institut d'Astrophysique Spatiale
George Washington University
Pierre and Marie Curie University
University of Hawaii at Manoa
The Open University
Institut d'Astrophysique Spatiale
Stockholm University
Western Michigan University
Space Telescope Science Institute
Jet Propulsion Laboratory
Institute of Low Temperature Science, Hokkaido
University
University of Gothenburg
University of Hawaii at Manoa
Max Planck Institute for Astronomy
Aarhus University
NASA Goddard Space Flight Center
The Open University
Osservatorio Astronomico di Palermo (INAF-OAPa)
University of Hawaii at Manoa
University of Hawaii at Manoa
Institute of Low Temperature Science, Hokkaido
University
KRIM
Le Sergeant
d'Hendecourt
Lee
Lemaire
Lahouari
Pierre and Marie Curie University
Louis
Yuan-Pern
Jean Louis
Ligterink
Martin
McGuire
Misselt
Muñoz-Caro
Nahon
Öberg
Orlando
Niels
Marie-Aline
Brett
Karl
Guillermo M.
Laurent
Karin
Thom
Osaka
Paardekooper
Perera
Rimola
Sanche
Shingledecker
Sibener
Strittmatter
Theulé
Thomas
Thorwirth
Tran
Turner
Vidali
Watanabe
Ziurys
Kazuya
Daniel
Thushara
Albert
Léon
Christopher
Steven
Peter
Patrice
Aaron
Sven
Katherine
Andrew
Gianfranco
Naoki
Lucy
IAS-CNRS-FRANCE
National Chiao Yung University
Observatoire de PARIS
Sackler Laboratory for Astrophysics, Leiden
Observatory
Harvard-Smithsonian Center for Astrophysics
NRAO / Caltech
University of Arizona
Center of Astrobiology (CAB)
SOLEIL
Harvard-Smithsonian Center for Astrophysics
Georgia Institute of Technology
Institute of Low Temperature Science, Hokkaido
University
Leiden University
Illinois Wesleyan University
Universitat Autonoma de Barcelona
University of Sherbrooke
University of Virginia
University of Chicago
Steward Observatory, University of Arizona
Aix-Marseille University
University of Hawaii
University of Cologne
Wellesley College
University of Hawaii at Manoa
Syracuse University
Hokkaido University
Arizona Radio Observatory, University of Arizona