PL.1
Comparing Chemistry in Microdroplets to that in Bulk Solution
Shibdas Banerjee1, Basheer Chanbasha1,2, Jae Kyoo Lee1, Hong Gil Nam3, Xin Yan1, and
Richard N. Zare1
1. Deparetment of Chemistry, Stanford University, Stanford, California 94305, USA
2. Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia
3. Center for Plant Aging Research, Institute for Basic Science (IBS), Daegu 42988, Republic of Korea and
Department of New Biology, DGIST, Daegu 42988, Republic of Korea
Most chemical reactions are conventionally run in bulk solvent. In sharp contrast, we have recently observed that
a reaction rate can be increased by a factor of a million or more in microdroplets [1-3]. For example, we studied
the redox reaction between 2, 6 dichlorophenolindophenol (DCIP) and ascorbic acid in fused droplets [1], and the
C-H bond activation in a Pomeranz–Fritsch synthesis of isoquinoline and Friedländer and Combes syntheses of
substituted quinolines in charged microdroplets produced by an electrospray process at ambient temperature and
atmospheric pressure [3]. In the case of isoquinoline and quinoline all of these reactions are known to take a long
time in bulk solution, ranging from several minutes to a few days, and to require very high concentrations of acid.
In contrast, we report appreciable yields on the millisecond timescale in charged microdroplets without the addition
of any external acid. Decreasing the droplet size and increasing the charge of the droplet both strongly contribute
to reaction rate acceleration, suggesting that the reaction occurs in a confined environment on the charged surface
of the droplet.
The exact general mechanism of the reaction rate acceleration in a microdroplet is not known to date, and it is
thought to involve numerous factors, such as evaporation, interfacial effects of diffusion and electric field, as well
as charged mnicrodroplet fission. The opportunity presents itself that microdroplet chemistry might be used to
advantage in preparative-scale synthesis. It is natural to wonder to what extent microdroplet chemistry serves as
a model of bulk solution chemistry but at a faster pace. We will present data showing that under certain conditions
the reaction products of microdroplets can markedly differ from those in the bulk.
References
1 Jae Kyoo Lee, Samuel Kim, Hong Gil Nam, and Richard N. Zare, "Microdroplet fusion mass spectrometry for fast reaction kinetics",
Proc. Natl. Acad. Sci. (USA) 112, 3898-3903 (2015).
[2] Jae Kyoo Lee, Shibdas Banerjee, Hong Gil Nam, and Richard N. Zare, “Acceleration of reaction in charged microdroplets”, Quart. Rev.
Biophys. Discov. 48, 437-444 (2015).
[3] Shibdas Banerjee and Richard N. Zare, “Syntheses of isoquinoline and substituted quinoline in charged microdroplets”, Angew. Chem.
Int. Ed. 54, 14795-14799 (2015).
23
PL.2
Imaging O2 Astrochemistry
Roy Scheidsbach and David H. Parker
Institute for Molecules and Materials, Radboud University Nijmegen, the Netherlands
Molecular oxygen, O2, is a fascinating molecule involved in many processes occurring on Earth and the
interstellar medium (ISM). Cold gases, which are observed in regions of the ISM where thermal desorption is
negligible, may arise from photo-desorption from icy grains, especially in regions with high UV flux. In this
study we carry out velocity map imaging1 (VMI) experiments on ultraviolet photo-desorption of O2 molecules
and O atoms from an O2-ice surface at 20K. The information we obtain should give more insight into similar
processes taking place at icy interstellar grains. We have recently completed our “ice-machine” apparatus which
combines the Velocity Map Imaging technique with an ultra-high vacuum ice surface setup with controlled
doping and surface analysis by thermal programmed desorption. Using state selective ionization of desorbed
molecules by REMPI and full 3-D velocity information
from the imaging technique it is possible to gain more
detailed insight into the processes occurring on ice surfaces.
A set of VMI images of nascent O(3P2) atoms produced by
laser desorption at 320 nm and 250 nm is shown in Fig 1.
At early time delays between desorption and probe, a plume
of O atoms (first O(3P), slightly later O(1D)) is observed as
it passes the detection laser pathway. With a slightly longer
time delay (2 µs), the O atom image begins to reveal a
higher velocity component which we believe is the
signature of electronically excited O2 (a1∆g) molecules2. At
the longer time delay (7.6 µs) the O atom plume has passed
and a clear signature of relatively cold O2 X(3Σg-) molecules
leaving the surface remains. At the shorter desorption
wavelength of 250 nm the O2 (a1∆g) signal is stronger than
at 320 nm. These observations and their underlying
processes will be described in more detail in this talk. We
acknowledge support by the NWO-CW TOP project
715.013.002 and collaboration with H. Linnartz (Leiden)
and H. Cuppen (RU).
Fig. 1 Raw VMI images of O(3P2) atoms ejected from a 20K O2-ice surface following laser desorption at 320
nm and 250 nm with the indicated time delay between desorption and detection 1.5 mm above the surface. The
various rings in the images are signatures of hot O(3P) atoms and O2 X(3Σg-) and (a1∆g) molecules.
References
[1] ATJB Eppink, DH Parker, Velocity map imaging of ions and electrons using electrostatic lenses: Application in photoelectron and
photofragment ion imaging of molecular oxygen, Review of Scientific Instruments 68, 3477-3484 (1997).
[2] Z Farooq, DA Chestakov, B Yan, GC Groenenboom, WJ van der Zande, and DH Parker, Photodissociation of singlet oxygen in the UV
region Physical Chemistry Chemical Physics 16, 3305-3316 (2014).
24
PL.3
The Role of Reagent Alignment
In Simple Surface Reactions
Kelvin Anggara1, Avisek Chatterjee1, Fang Cheng1, Si Yue Guo1, ZhiXin Hu1,2, Kai Huang1, Stephen J.
Jenkins3, Wei Ji2, Lydie Leung1, Miaomiao Luo1, Oliver MacLean1, Zhanyu Ning1, John C. Polanyi1,
Marco Sacchi3 and Chen-Guang Wang1,2
1 Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
2 Department of Physics, Renmin University of China, Beijing, China
3 Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
Scanning Tunneling Microsocopy (STM) has opened the way to the study of surface reactions a-molecule-ata-time, giving an impetus to the field of stereodynamics. Injecting an electron from the tip of the STM into
aligned and oriented adsorbates on semiconductor or metal is found to result in surface reaction involving the
selective rupture of adsorbate bonds, and directional recoil of the products. In this work the bond-selectivity
and directional-selectivity will be interpreted in terms of a two-electronic-state model of the dynamics. Recent
theory and experiment shows products recoiling directionally with chiral retention, and in specified cases either
walking or flying across the surface. The extent of in-plane product rotation can be used as a 'clock' against
which to time the sub-picosecond reaction dynamics. Stereodynamics at surfaces appears to offer rich future
possibilities.
25
PL.4
The dynamics of molecular interactions and chemical reactions at
metal surfaces: Testing the foundations of theory
Oliver Bünermann1, Hongyan Jiang1,Yvonne Dorenkamp1, Alexander Kandratsenka 1,2,
Svenja M. Janke1,2 Daniel J. Auerbach1,2 and Alec M. Wodtke1,2
1. Institute for Physical Chemistry, Georg August University of Göttingen, Tammannstrasse 6, 37077 Göttingen, Germany
2. Department of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
In 1929, Nobel Laureate Paul Dirac made comments to the effect that Chemistry had been solved. With the
advent of quantum mechanics “The underlying physical laws necessary for the mathematical theory of… …the
whole of chemistry are… …completely known…. However, on a practical level computational chemistry is still
in an early stage of development. Dirac went on: “the difficulty is only that the exact application of these laws
leads to equations much too complicated to be soluble.” Despite electrifying advances in computational power
since that time, Dirac is still right. The theory of chemistry requires approximations before theoretical
descriptions and predictions of chemical reactions can be made.
The advent of the Born-Oppenheimer Approximation led to the development of the standard model of chemical
reactivity where the electronically adiabatic potential energy surface for nuclear motion is derived and quantum
motion of the nuclei on that surface can be calculated. For simple gas phase reactions, this approach has become
an extraordinarily useful and reliable tool. For surface chemistry, additional approximations are commonly
made: 1) classical mechanics for describing nuclear motion, 2) density functional theory (usually at the
generalized gradient level) for calculating electronic states, 3) reduced dimensionality approximations and as
before 4) the Born-Oppenheimer approximation to separate electronic and nuclear degrees of freedom. I call this
collection of approximations the provisional model for surface chemistry as we in the field are still testing and
improving it.
In this talk, I will describe how a fruitful interplay between experiment and theory can lead to accurate atomicscale simulations of simple reactions at metal surfaces. I will describe the very significant challenges surface
chemistry presents including the problems of high dimensionality and the common failure of the Born
Oppenheimer approximation. As a concrete example, I will present results of a full dimensional theoretical
approach to hydrogen atom adsorption at a metal surface that includes the effects of Born-Oppenheimer failure.
This leads to an atomic scale view of H-atom adsorption at a noble metal.
References
Oliver Bünermann, Yvonne Dorenkamp, Hongyan Jiang, Alexander Kandratsenka, Svenja Janke, Daniel J. Auerbach and Alec M. Wodtke,
Electron-hole pair excitation determines the mechanism of hydrogen atom adsorption, Science 350, 1346 (2015).
Svenja Janke, Daniel J. Auerbach, Alec M. Wodtke, Alexander Kandratsenka, An accurate full-dimensional potential energy surface for HAu(111): Importance of nonadiabatic electronic excitation in energy transfer and adsorption, J. Chem. Phys. 143, 124708 (2015) .
Nils Bartels, Kai Golibrzuch, Daniel J. Auerbach and Alec M. Wodtke, The dynamics of molecular interactions and chemical reactions at
metal surfaces: Testing the foundations of theory, Annual Review of Physical Chemistry 66, 399 (2015).
26
PL.5
Reaction Dynamics Employing High-Dimensional, Ab Initio
Potential Energy Surfaces
Joel M. Bowman,1 Xiaohong Wang,1 Aryya Gosh1 and Paul Houston2
1. Department of Chemistry, Emory University, Atlanta, GA 30322 USA
2. School of Chemistry and Biochemistry Georgia Institute of Technology Atlanta, Georgia 30332 and
Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14852, USA.
I will review recent progress in developing full-dimensnioal, permutationally-invariant, potential energy
surfaces for complex polyatomic reactions. Illustrations of how these have been used in extensive quasiclassical
trajectory calculations of unimolecular reactions (mainly) will be given. The historically important dissociation
of H2CO, will be discussed, including a brief re-cap of “roaming”, work done with Arthur Suits [1]. A new PES
for this reaction has been developed and will be briefly described along with our assessment of why “roaming” is
still a major challenge for a simple constructive Transition State Theory. Recent work on the unimolecular
dissociation of the Criegee intermediate, syn-CH3CHOO, in collaboration with Marsha Lester [2] will be
presented, with a focus on two mechanisms for the high-energy dissociation [3], illustrated by the schematic
Fig. 1 Schematic of direct and indirect pathways for
syn-CH3CHOO dissociation to OH+CH2CHO
above. The isomerization of syn-CH3CHOO to vinyl hydroperoxide is also of current interest and some
predictions about mode-specificity will be given, based on a simple projection model [4]. Time permitting, I will
report a new potential energy surface for CH4 dissociation to H+CH3 and CH2+H2 and preliminary dynamics
calculations, stimulated by experiments of Heck, Zare and Chandler [5].
References
[1] D. Townsend, S. A. Lahankar, S. K. Lee, S. D. Chambreau, A. G. Suits, X. Zhang, J. Rheinecker, L. B. Harding and J. M. Bowman, The
roaming atom: Straying from the reaction path in formaldehyde decomposition Science 306, 1158-1161 (2004).
[2] N. M. Kidwell, H. Li, X. Wang, J. M. Bowman, and M. I. Lester, Unimolecular dissociation dynamics of vibrationally activated
CH3CHOO Criegee intermediates to OH radical products, Nature Chem., 8. 509-514 (2016).
[3] X. Wang and J. M. Bowman, Two Pathways for Dissociation of Highly Energized syn-CH3CHOO to OH Plus Vinoxy, J. Phys. Chem.
Lett. 7, 3359-3364 (2016).
[4] Y. Wang and J. M. Bowman, Mode-Specific Tunneling Using the Q im Path: Theory and an Application to Full-Dimensional
Malonaldehyde, J. Chem. Phys. 139, 154303 (2013).
[5] Heck, A. J. R.; Zare, R. N.; Chandler, D. W. Photofragment imaging of methane. J. Chem. Phys, 104, 4019-4030 (1996).
27
PL.6
Strong Laser Field Control of Photodissociation Stereodynamics
María E. Corrales1, Rebeca de Nalda2, and Luis Bañares1
1. Departamento de Química Física I (Unidad Asociada I+D+i al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de
Madrid, Madrid 28040, Spain
2. Instituto de Química Física Rocasolano, CSIC, C/ Serrano, 119, Madrid 28006, Spain
Experiments aimed at understanding ultrafast molecular processes are now routine, and the notion that
external laser fields can constitute an additional reagent is also well established. The possibility of externally
controlling a reaction with radiation increases immensely when its intensity is sufficiently high to distort the
potential energy surfaces at which chemists conceptualize reactions take place [1].
In recent experiments, we have studied strong laser field control scenarios of ultrafast molecular
photodissociation dynamics. The control has been exerted on different observables of the photochemical reaction,
such as quantum yields [2,3] and lifetimes [2] or even on fragment translational energies [3]. The case study
involves photodissociation of the polyatomic prototype methyl iodide (CH3I), whose ultrafast photodissociation
dynamics has been studied in our laboratory for some years both in the A-band [4,5] and B-band [6], under
strong femtosecond or picosecond near-IR laser pulses [2,3], The control is achieved by opening new strongfield-induced reaction channels [2] or by creating light-induced conical intersections and modulating the
potentials around them by light-induced potentials [3]. In particular, control of the fragment spatial distribution
(the stereodynamics) in the predissociation of methyl iodide has been achieved by using strong picosecond laser
pulses [7] and the results will be presented at the Conference.
References
[1] I. R. Solá, J. González-Vázquez, R. de Nalda, and L. Bañares, Phys. Chem. Chem. Phys. 17, 13183 (2015).
[2] M. E. Corrales, G. Balerdi, V. Loriot, R. de Nalda, and L. Bañares, Faraday Discuss. 163, 447 (2013).
[3] M. E. Corrales, J. González-Vázquez, G. Balerdi, I. R. Solá, R. de Nalda, L. Bañares, Nature Chem. 6, 785 (2014).
[4] R. de Nalda, J. Durá, A. García-Vela, J. G. Izquierdo, J. González-Vázquez, and L. Bañares, J. Chem. Phys. 128, 244309 (2008).
[5] A. García-Vela, R. de Nalda, J. Durá, J. González-Vázquez, and L. Bañares, J. Chem. Phys. 135, 154306(2011).
[6] G. Gitzinger, M. E. Corrales, V. Loriot, R. de Nalda, and L. Bañares, J. Chem. Phys. 136, 074303 (2012).
[7] M. E. Corrales, R. de Nalda, and L. Bañares, in preparation.
28
PL.7
A Stereodynamic Interview
Dudley Herschbach
Department of Chemistry and Chemical Biology, Harvard University
12 Oxford St, Cambridge, MA 02138, USA
At a symposium on chemical stereodynamics, it seems apt to include an interview, as that mode
emulates reactive molecular collisions. Now an octogenarian, I especially enjoy relating encounters with
the actors and ideas that hatched the field. Much about those encounters has appeared in reviews that
emerged from the stereodynamics symposia [1-3] in which I took part, those held in Jerusaleum (1986),
Santa Cruz (1990), Osaka (2004). The interview will aim to bring out “back stories” not in print, and to
emphasize prospects that are, in my view, ripe for further development. Also, I want to honor the memory
of two inspiring colleagues: Dick Bernstein [4] and Kent Wilson [5].
References
[1] R.B. Bernstein, D.R. Herschbach, and R.D. Levine, Dynamical Aspects of Stereochemistry, J. Phys. Chem. 91, 5365-5377 (1987).
[2] B. Friedrich, D.P. Pullman and D.R. Herschbach, Alignment and Orientation of Rotationally Cool Molecules, J. Phys. Chem. 95,
8118-8129 (1991).
[3] D. Herschbach, Chemical Stereodynamics: Retrospect and Prospect, Eur. Phys. J. D 38, 3-13 (2006).
[4] D.R. Herschbach, Richard Bernstein: Zestful Explorer of Collision Dynamics, J. Phys. Chem. 95, 7963 (1991).
[5] D. Herschbach, Kent R. Wilson: Inspiring Architect of Laser Chemistry, Nature 405, 902 (2000).
29
PL.8
Bimolecular and unimolecular transition state dynamics studied by slow electron velocity-map
imaging of cryogenically cooled anions (cryo-SEVI)
Daniel M. Neumark
Department of Chemistry
University of California
Berkeley, CA 94720
USA
Negative ion photoelectron spectroscopy has been successfully applied to the study transition states in
several benchmark bimolecular and unimolecular reactions. Recent advances in our laboratory have
significantly improved the energy resolution of this technique. We now trap and cryogenically cool
anions in an rf trap to approximately 10 K, then photodetach the ions and measure their photoelectron
spectrum using slow electron velocity-map imaging. The overall method, cryo-SEVI, yields
photoelectron spectra with sub-meV energy resolution for complex species such as polycyclic aromatic
hydrocarbon radicals, transition metal oxide clusters, and transition state species. This improved
resolution reveals previously inaccessible vibrational structure that provides new insights into the
spectroscopy and dynamics of the neutral species generated by photodetachment. Examples of recent
cryo-SEVI results will be presented, with particular emphasis on the transition states for the F + H2 and F
+ CH3OH reactions and new spectra that probe vinylidene→acetylene isomerization.
30
PL.9
Deep Decarbonization and Sustainable Development
Yuan T. Lee
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
During the long history of mankind, planet Earth seemed to be an infinitely large place. The earth was so
immense that the impact of human activities to the biosphere seemed quite negligible. But after the industrial
revolution and especially in the twentieth century things have changed dramatically. World population increased
from 1.5 billion to 6 billion in the twentieth century and has reached 7.3 billion this year. And with the
advancement of communication and transportation, the earth has shrunk in relative terms. This sudden transition
from “unlimited earth” to a “limited earth” has extremely significant consequences, yet the development of
human society, moving along the track of infinity for a long time, has not seemed to be able to adapt to the new
reality that the earth is “limited”. On the “limited earth”, perhaps the most important challenges for scientists are
problems related to the climate change and environmental degradation, together with unsustainable production
and consumption. Without immediate action and transformation, the survival of human society will be seriously
threatened.
This is the first time in human history that all human beings on Earth have been faced with learning to work
together and live together as one family in a global village – the time for finally realizing that the planet Earth on
which we live is only finite in space, capacity and natural resources. Our future depends entirely on how
effectively the entire world would function as a community. This is a necessary awakening – vital for the
survival and sustainable development of mankind. I believe that if we make the correct choice at this crossroads,
then the 21st century is likely to be marked as the great turning point, or great transition – the beginning of a new
era in the history of mankind.
31
PL.10
Molecular photofragmentation dynamics in the gas and
condensed phases: similarities, differences and opportunities
Michael N.R. Ashfold
School of Chemistry, University of Bristol, Bristol, U.K., BS8 1TS
Phenols and azoles are common chromophores in the nucleobases and the aromatic amino-acids that
dominate the near UV absorption spectra of many biological molecules. * excitations are responsible for
these strong UV absorptions, but such molecules also possess excited states formed from * electron
promotions. These * states typically have much smaller absorption cross-sections, but they can be of profound
photophysical importance. We have used photofragment translational spectroscopy (PTS) methods and
complementary ab initio theory to explore *-state mediated bond fission processes following UV excitation of
many heteroaromatic molecules in the gas phase [1], and ultrafast pump-probe studies to explore related
processes in a range of solvents [2]. This presentation will: (i) summarize photophysical insights gained from
PTS studies of pyrrole, phenol and related molecules in the gas phase [3-8], (ii) highlight the extent to which
such knowledge can inform our interpretation of ultrafast pump-probe studies of the UV photofragmentation of
similar molecules (e.g. thiophenols) in solution [9], and (iii) demonstrate how such solution phase studies offer a
means of exploring *-state mediated ring-opening of heterocycles like thiophenes and pyrones [10,11].
References
[1] See, e.g., M.N.R. Ashfold, et al., * excited states in molecular photochemistry, Phys. Chem. Chem. Phys. 12, 1218 (2010).
[2] See, e.g. G.M. Roberts et al., On the participation of photo-induced N–H bond fission in aqueous adenine at 266 and 220 nm: a
combined ultrafast transient electronic and vibrational absorption spectroscopy study, J. Phys. Chem. A 118, 11211 (2014).
[3] D.A. Blank, S.W. North and Y.T. Lee, The ultraviolet photodissociation dynamics of pyrrole, Chem. Phys. 187, 35 (1994).
[4] C.M. Tseng, Y.T. Lee and C.K. Ni, H atom elimination from the pi sigma* state in the photodissociation of phenol, J. Chem. Phys. 121,
2459 (2004).
[5] B. Cronin, et al., High resolution photofragment translational spectroscopy studies of the near ultraviolet photolysis of pyrrole, Phys.
Chem. Chem. Phys. 6, 5031 (2004).
[6] M.G.D. Nix, et al., High resolution photofragment translational spectroscopy studies of the near ultraviolet photolysis of phenol,
J. Chem. Phys. 125, 133318 (2006).
[7] T.N.V. Karsili, et al., O–H bond fission in 4-substituted phenols: S1 state predissociation viewed in a Hammett-like framework,
Chem. Sci. 4, 2434 (2013).
[8] S.J. Harris, et al., A multi-pronged comparative study of the ultraviolet photochemistry of 2-, 3- and 4-chlorophenol in the gas phase,
J. Phys. Chem. A 119, 6045 (2015).
[9] Y. Zhang, et al., Contrasting the excited state reaction pathways of phenol and para-methylthiophenol in the gas and liquid phases,
Farad. Disc. Chem. Soc. 157, 141 (2012).
[10] D. Murdock, et al., Transient UV pump-IR probe investigation of heterocyclic ring-opening dynamics in the solution phase: the role
played by n* states in the photoinduced reactions of thiophene and furanone, Phys. Chem. Chem. Phys. 16, 21271 (2014).
[11] D. Murdock, et al., Contrasting ring-opening propensities in UV-excited -pyrone and coumarin, Phys. Chem. Chem. Phys. 18, 2629
(2016).
32
PL.11
Differential steric effects in Cl + CHD3(v1=1, ǀJK〉) reactions:
Rotational-mode specificity and collisional energy dependency
Fengyan Wang,1,2 Huilin Pan,1 and Kopin Liu1,3
1. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
2. Department of Chemistry, Fudan University, Shanghai, China
3. Department of Physics, National Taiwan University, Taipei, 10617, Taiwan
The effect of the rotational excitations of CHD3(v1 = 1, ǀJK〉) in reaction with the Cl atom was investigated in
a crossed-beam, product-imaging experiment over the collisional energy (Ec) range of 2 – 8.6 kcal mol-1 [1, 2].
We found that the initial rotational-state selection of the vibrationally excited reactants exerts significant effects
on the reaction rate; yet, the more detailed product state and angular distributions are nearly invariant − a surprising
result that defies conventional wisdom. This phenomenon have been termed a “loss of memory” effect, in which
the reactivity is governed by how the reactants reach the transition state, thus depending on the initial rotational
states. Once the transition state is attained, the memory of of the initial state ǀJK〉 is lost, leading to the same product
distributions [1, 3].
Further studies of this reaction with actively aligned CHD3(v1 = 1, ǀJK〉) reactants, however, revealed very
prominent and distinct polarization-dependent differential cross sections (PDDCSs) for the initial ǀJK〉=ǀ10〉 state
[4, 5] and rather moderate PDDCSs for ǀJK〉=ǀ1±1〉 [4, 6, 7]. Hence, the origin of the “loss of memory” effect can
be traced to the stereo-averaging of all possible collision geometries, rather than the memory-loss of the initial
selection of rotational states as we originally conceived. Moreover, the stark contrast between the two sets of
PDDCSs for states with the same J = 1 but different K quantum number (the projection of J to the C3v symmetry
axis) is unexpected. Clearly, how the molecules rotate in the molecular frame (a spinning or a tumbling motion)
can have enormous effects on the stereo-specific reactivity in the space (or the laboratory) frame. The implications
of this intriguing finding to stereodynamics will be discussed.
References
[1] R. Liu, F. Wang, B. Jiang, G. Czako, M. Yang, K. Liu and H. Guo, Rotational mode soecificity in the Cl + CHD3  HCl + CD3 reaction,
J. Chem. Phys. 141, 074310 (2014).
[2] F. Wang, H. Pan, and K. Liu, Imaging the effect of reactant rotations on the dynamics of Cl + CHD3(v1=1, ǀJK〉) reaction, J. Phys. Chem.
A 119, 11983 (2015).
[3] H. Pan, Y. Cheng and K. Liu, Rotational mode specificity in Cl + CH4(v3=1, ǀJNl〉): Role of Reactant’s vibrational angular momentum, J.
Phys. Chem. A 120, 4799 (2016).
[4] F. Wang, J.-S. Lin and K. Liu, Steric control of the reaction of CH stretch-excited CHD3 with chlorine atom, Science, 331, 900 (2011).
[5] F. Wang, K. Liu, and T. P. Rakitzis, Revealing the stereospecific chemistry of the reaction of Cl with aligned CHD3(v1=1), Nat. Chem. 4,
636 (2012).
[6] F. Wang and K. Liu, Differential steric effects in Cl reactions with aligned CHD3(v1=1) by the R(0) and Q(1) transitions. I. Attacking the
excited C-H bond, J. Chem. Phys. (accepted, 2016).
[7] F. Wang and K. Liu, Differential steric effects in Cl reactions with aligned CHD3(v1=1) by the R(0) and Q(1) transitions. II. Abstracting
the unexcited D-atoms, J. Chem. Phys. (accepted, 2016).
33
RB.1
The Use of Velocity Mapped Ion Imaging to Study Inelastic
Scattering.
David Chandler
Combustion Research Facility, Sandia National Laboratory, Livermore CA 94550, United State.
Stereodynamics is the study of the impact of orientation and alignment of atoms and molecules on
reactivity and the production of alignment and orientation of atoms and molecules from reactivity. One tool
that has been instrumental in the observation of alignment and orientation has been the ion imaging
technique with all of its variations. The use of polarized laser beams to resonantly produce ions that whose
positions are measured allows one to measure, with little effort, the alignment or orientation of scattered
products for a particular scattering velocity.
Crossed molecular beam studies utilizing velocity mapped ion imaging have provided the first three and
four vector-correlated studies of collisional dynamics. The crossed beams provide a definition of the
incoming velocity vector and the ion imaging measures the alignment or orientation of the product for each
product scattering velocity. When the reactants are produced in a manner that provides an alignment or
orientation then four vectors are correlated and the dynamics of the collision is investigated with extreme
precision. This provides a very stringent test for the theories of scattering and reactivity. Recent studies
involving laser preparation of oriented species will be highlighted as well as previous studies that highlight
the utility of this technique for the study of stereodynamics. In particular the scattering of laser prepared
and oriented NO(A N=2) with Ne will be discussed.
34
RB.2
Stereodynamics: From Elementary Processes to Macroscopic
Chemical Reactions and their Interconnections
Toshio Kasai1,2
1. Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan
2. Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan
This talk aims at discussing two facets on stereodynamical behaviors in chemical reactions. [1,2] One manifests
in elementary processes at the molecular level, and the other may be observed as non-linear, transport-limited, or
sudden-change behaviors in the macroscopic system with time and space complexity. First, we show usefulness
of the electrostatic hexapole state-selector, followed by some experimental examples of the steric effect found in
simple reactions that consist of three or four atoms, then in more complex systems like gas-surface reactions. [3]
We finally would like to search for a bridge to interconnect between the two aspects of stereodynamics and/or
reaction dynamics. The interconnection of quantum and classical mechanics is presented as a relevant view by
introducing a topological picture in order for interpreting collisional decoherence phenomenon.
1. Versatility and usefulness of the electrostatic hexapole state-selector: We provide some examples for the
versatility of the hexapole as pure radical beam sources, non-destructive selection of isomers, and as a tool for
probing transition state region of the Cl + HCl reaction.
2. Stereodynamics of A + BC and AB + CD reactions: we show steric effects in energy transfer reactions of
metastable atoms or the fast electron with oriented-molecules, such as CH3Cl, as three-atom reactions. [4] We also
give an exampl for a unexpected reaction pathway observed in the oriented-OH + HBr four-atom reaction.
3. Stereodynamics of heterogeneous reactions at surfaces: The dissociative adsorption of CH3Cl on Si surface
occurs via precursor states. We find that there is no steric effect at the lower surface temperatures as expected, but
we clearly see the Cl-end preference to the CH3-end collision above 280 K. This would be a good example for the
steric effect appeared in surface reaction. [5]
4. Plant respiration reaction and non-Arrhenius behavior: For reaction dynamics in macroscopic chemical
reactions, the temperature dependence of the rates of cellular respiration of Camellia Japonica was investigated
using isotopically enriched oxygen, 18O2. We find that respiration should be written as eq. 2 but not as eq.1 because
this reactions is an auto-catalytic reaction represented as A + B → 2B, where water (H2O) plays an important key
role. The observed deviations from Arrhenius law on the temperature dependence of the respiration rate is analyzed
and interpreted with the aid of theory and the MD simulation in view of water micro-solvation network.
C6H12O6 + 6O2
→ 6CO2 + 6H2 O
(1)
(2)
C6H12O6 + 618O2 + 6H2 O → 6CO2 + 12H218O
5. Collisional decoherence to interconnect the wave-particle property: A physico-mathematical picture is
presented for explaining the unexpectedly large decoherence cross section observed in the scattering experiment
of coherent-NO beam with Ar. This topological picture consists of a stereographic projection and the cusp
catastrophe theory of Thom, and it enables us to clarify the origin of the collisional decoherence and to predict
sudden changes of the wave-phase collapse due to a network interaction in the macroscopic system.
The orientation or alignment of molecules thus affects reaction dynamics in dramatic ways. Accordingly, we
do expect the control of chemical reactions by manipulating molecular orientation. In such way, it is not necessary
for us to use any new catalysts, instead, we simply control activation energy barrier by controlling molecular
orientation of reagents in advance of chemical reactions. Therefore, this orientation-controlled reaction may be
called as “catalytic reaction without any material catalyst”.
References
[1] T. Kasai, D. -C. Che, M. Okada, P. -Y. Tsai, K. -C. Lin, F. Palazzetti, V. Aquilanti, Directions of chemical change: experimental
characterization of the stereodynamics of photodissociation and reactive processes, Phys. Chem. Chem. Phys. (Perspective) 16, 9776, (2014).
[2] T. Kasai, D.-C. Che, P.-Y. Tsai, K.-C. Lin, Reaction dynamics with molecular beams and oriented molecular beams: A tool for looking
closer to chemical reactions and photodissociations, J. Chin. Chem. Soc, 59, 561, (2012).
[3] K. Kuwata and T. Kasai, Steric Effects in Small Radical Formations, in ‘The Chemical Dynamics and Kinetics of Small Radicals Part II’,
ed. by K. Liu and A. Wagner, Advanced Series in Physical Chemistry (World Scientific), Vol. 6, 842-935 (1995).
[4] T. Kasai, T. Matsunami, T. Fukawa, H. Ohoyama, K. Kuwata, Effect of Molecular Orientation on Indirect Ionization by Electron Impact
of CH3Cl in the |111> Eigenstate, Phys. Rev. Lett., 70, 3864 (1993).
[5] M. Okada, T. Kasai, Molecular Orientation Effects in Gas-Surface Dynamical Processes, Euro. Phys. J. B, 75, 71 (2010).
[6] T. Kasai and K.-C. Lin, Coordinate analysis for interpreting the decoherence in the coherent-NO with Ar collision: A physicomathematical picture using the stereographic projection and the cusp catastrophe, J. Chin. Chem. Soc., in press (2016).
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