https://doi.org/10.1140/epja/i2008-10692-4
Regular Article - Experimental Physics
Revised spin-parity assignment and a new interpretation of the high-spin isomer in 151Er
1
Department of Physics, Osaka University, Machikaneyama-machi 1-1, Osaka 560-0043, Toyonaka, Japan
2
RIKEN, Hirosawa 2-1, Saitama 351-0198, Wako, Japan
3
Center for Nuclear Study, University of Tokyo, Hirosawa 2-1, Saitama 351-0198, Wako, Japan
4
Cyclotron and Radio-isotope Center, Tohoku University, Aoba 6-3, Sendai, 980-8578, Aobaku, Japan
5
Department of Physics, Tohoku University, Aoba 6-3, Sendai, 980-8578, Aobaku, Japan
* e-mail: odahara@phys.sci.osaka-u.ac.jp
Received:
20
July
2008
Revised:
7
October
2008
Published online:
15
December
2008
The high-spin isomer in 151Er ( E
x = 10.3 MeV, T
1/2 = 420 ns) has been studied by the 116Sn ( 40Ar , 5n) 151Er reaction at 197MeV. From the coincidence relations, a new transition with an energy of 1514keV was found. This finding requires the revision of the spin-parity assignment from previous 67/2- to 61/2+ or 65/2- . The 61/2+ assignment is the one which was predicted by the deformed independent particle model as an isomer with a large oblate deformation (
= - 0.17) of the
configuration. The isomerism may be attributed to the sudden shape change of the isomer from the nearly spherical shape of the lower-spin yrast states to the oblate shape.
PACS: 21.60.Cs Shell model – / 23.20.Lv transitions and level energies – / 27.70.+q 150
A
189 – / 29.30.Kv X- and
-ray spectroscopy –
© SIF, Springer-Verlag Berlin Heidelberg, 2009