Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Early onset of deformation in the
neutron-deficient polonium isotopes identified
by in-source resonant ionization laser
spectroscopy
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios, W. Dexters, M.D. Seliverstov, A.N. Andreyev,
S. Antalic, A.E. Barzakh, B. Bastin, J. Büscher, I.G. Darby,
D.V. Fedorov, V.N. Fedosseyev, K.T. Flanagan, S. Franchoo,
S. Fritzsche, G. Huber, M. Huyse, M. Keupers, U. Köster,
Yu. Kudryavtsev, E. Mané, B.A. Marsh, P.L. Molkanov,
R.D. Page, A.M. Sjoedin, I. Stefan, J. Van de Walle, P. Van
Duppen, M. Venhart, S.G. Zemlyanoy, M. Bender, P.-H. Heenen
Outline I
Polonium
charge radii
T.E. Cocolios
1
Shape coexistence in the polonium isotopes
2
In-source laser spectroscopy at ISOLDE
CERN’s Isotope Separator On-Line DEvice
Shape coexistence in the neutron-deficient 84 Po isotopes
3
Conclusions & Outlooks
Conclusions
Outlooks
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Outline
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
1
Shape coexistence in the polonium isotopes
2
In-source laser spectroscopy at ISOLDE
3
Conclusions & Outlooks
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Chart of the nuclides
A large world to explore
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Shape coexistence
in Pb isotopes
Polonium
charge radii
Shape coexistence =
proximity of spherical
and/or deformed shapes(s)
at low energy (E < few
MeV)
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
186 Pb:
most dramatic
examples where the three
lowest lying states are 0+
states of three different
shapes within less than
700 keV.
Conclusions &
Outlooks
Conclusions
Outlooks
A.N. Andreyev et al., Nature 405(2000)430
Shape coexistence
in Hg isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Evidence for shape
coexistence in
systematic energy
levels: flat behaviour
of the spherical
states against
parabolic intrusion
of the deformed
states with a
minimum at
mid-shell N = 104.
Shape coexistence
in Po isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
From shape coexistence to configuration mixing
From N = 126 down, vibrational behaviour with parabolic
intrusion of 0+
⇒ shape coexistence;
From N = 116 down, first 2+ , 4+ , . . ., go down with
intruding configuration
⇒ configuration mixing?
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Shape coexistence
What are the observables
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
√
low-energy excited 0+ state in even-even nuclei;
∼ low-energy excited structure issued from coupling to those
states in odd-A nuclei;
? shape of the ground state ⇒ charge distribution δhr 2 i;
? excitability of the structure and excited levels quadrupole
moments ⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒
transfer reactions.
Outline
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
1
Shape coexistence in the polonium isotopes
2
In-source laser spectroscopy at ISOLDE
CERN’s Isotope Separator On-Line DEvice
Shape coexistence in the neutron-deficient 84 Po isotopes
3
Conclusions & Outlooks
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
CERN ISOLDE
Isotope Separator On-Line DEvice
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
CERN ISOLDE
Isotope Separator On-Line DEvice
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
CERN ISOLDE
Isotope Separator On-Line DEvice
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Laser ionisation of polonium
Light in the dark
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios, B.A. Marsh et al., NIMB 266(2008)4403
Challenges of a radioactive element
No stable isotope ⇒ no off-live developments possible;
3 laser ionization schemes were successfully developed;
s-electron has the necessary overlap with the nucleus.
In-source laser spectroscopy of Po
even-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
from A = 192 up to A = 218;
from T1/2 = 33 ms up to
T1/2 = 3 yr;
from 0.3 ion·s−1 to over 107
ion·s−1 ;
using α, β, γ and ion (FC)
counting.
In-source laser spectroscopy of Po
even-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
from A = 192 up to A = 218;
from T1/2 = 33 ms up to
T1/2 = 3 yr;
from 0.3 ion·s−1 to over 107
ion·s−1 ;
using α, β, γ and ion (FC)
counting.
In-source laser spectroscopy of Po
even-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
from A = 192 up to A = 218;
from T1/2 = 33 ms up to
T1/2 = 3 yr;
from 0.3 ion·s−1 to over 107
ion·s−1 ;
using α, β, γ and ion (FC)
counting.
In-source laser spectroscopy of Po
odd-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
A = 191 to
A = 211;
T1/2 = 22 ms to
T1/2 = 102 years;
0.01 to over 107
ion·s−1 ;
long-lived
high-spin
13 +
isomers.
2
In-source laser spectroscopy of Po
odd-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
α decay of
195
Po
. . . serendipity at play
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Rich α decay
the α decay of the odd-A polonium isotopes has a rich
structure, revealing the importance of shape coexistence;
a large amount of data on the poorly-known isotope
was recorded during the study on charge radii.
195 Po
α decay of
195
Po
. . . serendipity at play
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
identification of α-γ
coincidences;
conversion coefficients
extracted from branching
ratios;
E 0 components and decay
hindrance factors permit
spin assignment in many
cases.
α decay of
195
Po
. . . serendipity at play
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios et al., JPG 37(2010)125103
β decay of
199
Po
. . . putting a finger on trouble. . .
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
β decay of
199
Po
. . . putting a finger on trouble. . .
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
β decay of
199
Po
. . . and trying to fix it
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios, Ph.D. Thesis (app. B2), KULeuven (2010)
http://fys.kuleuven.be/iks/ns/phd-master-theses
β decay of
199
Po
. . . and trying to fix it
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
A linear
combination of
spectra can yield a
“purified” spectrum.
No γ-γ coincidence
are available to build
up a level scheme.
191
Po
Pushing the limits of the technique
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
191 Po
with only 0.01 ion·s−1
very limited production
rates due to limited cross
section and short half lives;
sufficient resolution for
clean identification via α
decay;
In-source laser spectroscopy of Po
odd-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
In-source laser spectroscopy of Po
odd-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
In-source laser spectroscopy of Po
odd-A isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Extracting charge radii
King at play again
Polonium
charge radii
A0 − A
· (me ν + KSMS ) + 0.932 · F · δhr 2 i
AA0
A0 − Aref 0
F2
F2
· µδν1AA + ref
· KSMS1
· KSMS2 −
=
0
F1
Aref Aref
F1
0
δν AA =
T.E. Cocolios
Shape
Coexistence
µδν2AA
0
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios, W. Dexters, M.D. Seliverstov
et al., PRL 106(2011)052503
Large-scale atomic calculation by S. Fritzsche (GSI)
F and KSMS have been calculated;
if the y intercept is left free, χ2ν ∼ 1 can be reached
⇒ good
F2
F1
but systematic uncertainty on KSMS .
δhr 2 i
even-A isotopes
Polonium
charge radii
0
T.E. Cocolios
δν AA =
A0 − A
· (me ν + KSMS ) + 0.932 · F · δhr 2 i
AA0
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
T.E. Cocolios, W. Dexters, M.D. Seliverstov et al., PRL 106(2011)052503
δhr 2 i
all isotopes
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
M.D. Seliverstov, T.E. Cocolios et al., in preparation
δhr 2 i
. . . compared to the neighbouring nuclei
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
δhr 2 i
. . . compared to the neighbouring nuclei
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Electromagnetic moments
. . . magnetic dipole moments
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Electromagnetic moments
. . . electric quadrupole moments
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Deformation
Consistency check in the β2 parameter
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Outline
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
1
Shape coexistence in the polonium isotopes
2
In-source laser spectroscopy at ISOLDE
3
Conclusions & Outlooks
Conclusions
Outlooks
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Conclusions I
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
from the in-source laser spectroscopy work
clean beams of polonium are available (less than 1% contamination
in beams of 200 Po);
δhr 2 i deviate early and strongly from the spherical droplet model;
⇒ large mixing between the ground and intruder configurations;
some uncertainties on the spins challenge the previous nuclear
spectroscopic conclusions.
Conclusions II
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
concerning shape coexistence around Z = 82
√
low-energy excited 0+ state in even-even nuclei;
√
low-energy excited structure issued from coupling to those states in
odd-A nuclei;
√
shape of the ground state;
? excitability of the structure and excited levels quadrupole moments
⇒ Coulomb excitation;
? single-particle strength in the different energy levels ⇒ transfer
reactions.
Outlooks
Things to look forwards to. . .
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Shape coexistence in Po
determine the spins of the most neutron-deficient isotopes with a
higher resolution technique (CRIS);
Coulomb excitation of 196,198,200,202 Po at REX-ISOLDE with MiniBall
to determine E 2 matrix elements and quadrupole moments
(N. Kesteloot and B. Bastin);
HIE-ISOLDE opens new opportunities for transfer reactions on those
nuclei.
Coulomb excitation of
courtesy of B. Bastin
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
200
Po at MiniBall
CRIS
Collinear Resonant Ionization Spectroscopy
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
CRIS concepts
Collinear ⇒ Doppler compression of the velocity
distribution for resolution.
Resonant Ionisation ⇒ efficient selection of the beam of
interest for sensitivity.
CRIS
Collinear Resonant Ionization Spectroscopy
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks
Achievements
CRIS is being developped and tested at CERN ISOLDE.
vacuum of ∼ 10−9 mbar achieved at the interaction region.
⇒ non-resonant background suppressed by 1:50 000 on-line.
Further suppression can be achieved if ionising ions to a X++
state.
Collaboration
Polonium
charge radii
T.E. Cocolios
Shape
Coexistence
In-source
spectro
ISOLDE
Polonium
Conclusions &
Outlooks
Conclusions
Outlooks