???????????? ?????????????? ??????? ? ??????????????? ???? ? ????????????? ?? ISOLDE (??????? Tl ? Po)

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???????????? ?????????????? ??????? ?
??????????????? ???? ? ????????????? ?? ISOLDE
(??????? Tl ? Po)
A.E. Barzakh, D.V. Fedorov, V.S. Ivanov, P.L.
Molkanov, M.D. Seliverstov, Yu.M. Volkov
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IS 466 Identification and systematical studies
of the electron-capture delayed fission (ECDF) in
the lead regionPart I ECDF of 178,180 Tl
PhysicsWorld.com 10.12.10 IOP site ScienceNews
02.10.10 Scientific American 01.12.10 NatureNews
01.12.10
IS 456 Study of polonium isotopes ground state
properties by simultaneous atomic- and
nuclear-spectroscopy
ISOLDE Proposal Shape coexistence in the
lightest Tl isotopes studied by laser
spectroscopy
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1. Delayed fission in light Tl isotopes
ionizer
Laser beams
Mass separator
target
protons
Laser Ion Source (LIS)
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ionization efficiency 15
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E. Ye. Berlovich and Yu. N. Novikov, Phys. Lett.
B29, 155 (1969)
Two areas in the nuclear chart were identified
where DF is experimentally accessible the U
region and a region near the very
neutron-deficient Pb isotopes.
N/Z 1,25 for 180Hg, in contrast to a typical
ratio of N/Z 1,551,59 in the U region.
QEC(180Tl) - Bf (180Hg) 0.6 MeV (calculation)
(? Dubna 1992)
QEC(178Tl) - Bf (178Hg) 1.9 MeV (calculation)
QEC(182Tl) - Bf (182Hg) -0.5 MeV (calculation)
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In total, approximately 1200 singles ECDF decays
of 180Tl were detected, 350 of which being
observed as double-fold fission-fission
coincident events.
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180Tl
A new ECDF branching ratio of PECDF3,6(7)10-5
was deduced for the parent nucleus 180Tl, which
is much higher and much more precise than the
previously estimated value of PECDF10-(71)
(Dubna, 1992).
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In low-energy fission (including ß- or EC-delayed
fission) for nuclei from Fm to U asymmetric
fission dominate over symmetric fission due to
influence of doubly magic 132Sn. Below Th (Th,
At) only symmetric fission has been found.
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P. Möllers calculations (2D projection of the
total 5D picture)
mass asymmetry at the bottom of the valley is
108/72 (rather close to the observed 100/80
value)
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2. Shape coexistence in light Po isotopes
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Po
Pb
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Photoionization scheme for Po
Detection Faraday Cup a-detection
(Windmill) ß-detection (tape-station) ?-detection
(tape-station)
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Isotope shift d?A,A d?A,A F ?A,A
(NMSSMS)A,A
Changes in rms charge radius ?A,A dltr 2gt
C2dltr 4gt 0.93 dltr 2gt
T1/2 33 ms lt1 ion/s
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King plot ?s A,A ??A,A AA/(A-A) ?s?1 vs
?s?2
Calculations for Po F255 29140 MHz/fm2 F843
-12976 MHz/fm2 F843/F255 0.44
Mass shifts sum
Slope gives F factors ratio F843/F255 0.45(3)
from King plot
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even-even isotopes
dltr2gt, fm2
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Angular-momentum projected configuration-mixing
method starting with Skyrme interaction SLy4 in
the mean-field channel and a density-dependent
zero-range pairing force (discretized
Hill-Wheeler equation without any additional
parameters)
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The increasing softness of the deformation energy
surfaces, when going down from 210Po to 194Po,
leads to collective ground-state wave functions
of increasing spread over oblate, prolate and
spherical shapes. For 192,190Po, the ground-state
wave function becomes centered around an oblate
minimum in the deformation energy surface.
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odd isotopes
spherical nuclei
A I b
191 1,5 0,26
191m 4,5 0,25
193 1,5 0,19
193m 6,5 0,2
195 1,5 0,16
195m 6,5 0,13
197 1,5 0,11
197m 6,5 0,11
deformed nuclei
strong coupling (at large deformation) KI
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DM deformations fairly correspond to Qs for 3/2-
Po isomers
and completely disagree with Qs for 13/2 Po
isomers
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effect of deformation?
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Calculations rotor-plus-quasiparticle model with
b(DM) (negative) deformations
fair agreement!
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Calculations rotor-plus-quasiparticle model with
b(DM) (negative) deformations
fair agreement for Qs but great overestimation
for ms
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Qualitative estimation mixing of spherical
(shell model) and deformed (rotor-plus-quasiparti
cle model) configurations.
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3. Shape coexistence in light Tl
isotopes (proposal)
?
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?
regions of interest
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• ??????
• ?????????? ???????????? ??????? ???????????????
  ???? ?????? Z82. ??????????, ?????????? ???
  ??????? ???? Po, ???????????????, ? ?????????, ?
  ???????????? ?????????? ??????????? ?
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  ?????????? ????????? ???????? Po, ??? ??????? ???
  ???????? ???? ????????? ?????? ?? ????? ??????
  ??????-????.
• ??????? ??????????? ?????? ?? ????????????????
  ???????? ? ????????????? ??????? ????????
  ???????? Po ? ?????????????? ??????
  ?????-????-???????????? ? ???????????? ??????
  ?????????? ??????????? ? ???????????????
  ????????????.

1. ???????????? ????????????? ? 180Tl ?????
   ?????????????? ??????? (ECDF), ??????????
   ??????????? ?????? ??????? (PECDF3,6(7)10-5)
   ??????? ??? ???? ?? ????? ????? N/Z. ??????????
   ?????, ??????????? ??????? ?????????????
   ??????? 180Hg, ?? ?????????, ??? ? ?????????????
   ???????, ? ???????? ?????????? ????????. ???
   ???????? ??????? ???????? ????????? ????????
   ???????????????? ???????????? ?????? ???????.

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1. ? ???????? ???????? ??????????????? ???? ??????
   Z82, ? ????? ??? ????????? ????????????? ????
   180Tl, ??????????? ??? ?????????? ????????? ???
   ?????????????? ?????????????? ???????, ??????????
   ???????? ???????-?????????????????? ????????????
   ??????? ???????? Tl, ?????? ????????? ???
   ?184207 ????????????? ????????? ?? ????, ? ???
   ?178183 ?? ISOLDE. ???????????????
   ???????????? (??? ?? ????, ??? ? ?? ISOLDE)
   ??????????????? ?? ?????????????? ???????
   ???????).

1. ?????? ???????-?????????????????? ????????????
   At ????? ????? ????????? ???????? ??? ??????????
   ????????. ????????-?????????? ??????? At
   ?????????????? ????????? ??? ??? ?????? ?
   ???????? ?????????????? ???????, ??? ? ???
   ??????????? ???????????? ??????????????? ????.