Shape-coexistence in Pb isotopes

1
Electromagnetic moments for isomeric states in
nuclei far from stability
NIPNE Bucharest ? INFN LNL Legnaro
10 experiments _at_XTU -
Tandem Legnaro
Detailed studies of isomeric states ns - µs
? lifetimes and decay schemes ?
g-factors ? spectroscopic quadrupole moments
2
Nuclear moment measurements Dedicated
experiments - Hyperfine interactions TDPAD
Time Differential Perturbed Angular Distribution
Method

• NIPNE Bucharest new isomers, g, Qs
  nuclei near stability
• INFN LNL XTU Tandem accelerator
• Heavy ions pulsed beams ?T2
  ns Trep 200 ns 6.4 µs
• GAMIPE beam line
• g factors Hext ? ? ?L g ?N Hext
  /h Cubic crystalline lattice
• Qs Electric Field Gradients
  Noncubic crystalline lattice
• ?Q QsVzz / 4I(2I-1)h Vzz EFG
  (Probe Host) calibrated

3

• A130 shape evolution
• 136Pr 6
  T1/2 g Nucl. Phys. A 603,
  50 (1996)
• 129,131Ce 9/2-
  g Qs Nucl.
  Phys. A 633, 459 (1998)
• 130Ce 7-
  Qs Phys. Rev. C 60,
  024316 (1999)
• A180 K isomers
• 175W 7/2-
  g Phys. Lett. B 495, 289
  (2000)
• 176W 14
  T1/2 g Qs Phys. Lett. B 541,
  219 (2002)
• Shape coexistence Pb
• 191Pb 29/2- 33/2
  T1/2 AIP Conf. Proc. 831,
  278 (2006)
• 193Pb 29/2- 21/2- 33/2
  T1/2 g Qs Eur. Phys. J. A 20, 191
  (2004)
• Phys. Rev. C 70, 034305 (2004)
• 192,194Pb 8 11- 12
  T1/2 Qs Acta Phys.Pol.B38,1249
  (2007)
• 
  Phys. Lett. B
  2007 in press
• 188Pb 11- 12
  g LNL Ann. Rep. 2006, p. 33

4
176W 14 isomer T 1/2 35(10) ns

High K states E? transitions ?
?K ? degree of K-forbiddenness
f? (T1/2? /T1/2W) 1/? usually f?100
f? ? 2.3 (917 keV) 3.6 (945 keV)
LNL 164Dy(16O,4n)176W 83 MeV
?T2 ns Trep800 ns
B. Crowell et al., PRL 72, 1164 (1994)
5
MI Pb host Hext 27.5 kG
QI Tl host
gexp (14, 176W) 0.462 (11) gcalc (14)
0.475 (15)

• 14 ? 7/2 404 9/2- 514
• ? 5/2- 512 7/2 633

Qs (14, 176W) 6.0 (7) eb Qo 7.4 (9) eb
?2 (14) 0.29(4)
gR (14) 0.269(34)
g factor M. Ionescu-Bujor et al., Phys.
Lett. B 495, 289 (2000) Qs
M. Ionescu-Bujor et al., Phys. Lett. B 541, 219
(2002)
6

Shape coexistence in Pb isotopes
Isomers ns - µs ?
12 ? (1i13/22) 11 ?
(3s1/2-21i13/21h9/2) 8 ?
(1i13/2 1h9/2-1)
Potential energy surfaces Z82
188Pb
190Pb

0p-0h




2p-2h
192Pb
194Pb


4p-4h


Static moments ?
Qs M. Ionescu-Bujor et al., Phys. Lett. B (2007)
in press
D. Karlgren et al., PRC 73, 064304 (2006)
7
168Er (28Si, 4n) 192Pb 143 MeV pulsed ?T
2 ns Trep 3.2 ?s
8
11 ? (3s1/2-21i13/21h9/2) ? 9 ?
(2f5/21i13/2)
8 ? (3s1/2-2 1h9/22) ? 6 admixture
intruder
9 ? (2f5/21i13/2) ? 7 ?
(3s1/21i13/2)
9
192,194Pb TDPAD QI Bi crystalline
lattice
Vzz(PbBi) 1.39(10) 1021 V/m2
Qs ? 0.32 (4) eb
0.48 (3) eb
Qs ? 2.9 (3) eb
3.6(4) eb
10
12 ?(1i13/2-2) ?2 ?
0.02 11 ? (1i13/21h9/2) ?2 ? 0.12
PQ Pairing quadrupole model
PQ TAC Magnetic rotation
S. Frauendorf, NPA 677, 115 (2000)
12
11

• HFB
• N.Smirnova et al., PLB 569, 151
  (2003)
• IBM
• V. Hellemans , PRC 71, 034308
  (2005)

11
Qo (11, 192Pb) ? shape mixing
M. Ionescu-Bujor et al., Phys. Lett. B (2007),
doi 10.1016/j.physlettb.2007.05.002
11
188Pb triple shape coexistence
12 spherical ?(1i13/2)2 11 oblate ?
(1i13/2 1h9/2) 8 prolate ? ( 1i13/2 1h9/2-1)


G.D.Dracoulis et al. , PRC 67, 051301(R) (2003
LNL XTU Tandem ? TDPAD experiments in
progress g
factors 12 11- M. Ionescu-Bujor
et al., LNL Ann. Rep. 2006, INFN-LNL-217(2007),
p. 33
12
NIPNE Bucharest M. Ionescu-Bujor, A.
Iordachescu, D. Bucurescu,
N. Marginean, C.A. Ur, G. Suliman, C.
Rusu
Collaborations INFN Padova, INFN Legnaro,
Bonn, Leuven, Sao
Paolo, Sofia, Surrey