Revised spin-parity assignment and a new interpretation of the high-spin isomer in 151Er

T. Fukuchi; T. Hori; T. Masue; K. Tajiri; A. Sato; T. Furukawa; A. Odahara; T. Shimoda; Y. Wakabayashi; Y. Gono; T. Suzuki; M. Ukai; T. Wakui; A. Yamazaki; Y. Miyashita; N. Sato; M. Tateoka; M. Ohguma; T. Shinozuka; T. Koike; K. Shirotori; Y. Miura; S. Kinoshita; Y. Ma; Y. Y. Fu; H. Tamura

doi:10.1140/epja/i2008-10692-4

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2023 Impact factor 2.6

Hadrons and Nuclei

Eur. Phys. J. A (2009) 39: 49-51
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

T. Fukuchi¹, T. Hori¹, T. Masue¹, K. Tajiri¹, A. Sato¹, T. Furukawa², A. Odahara¹^*, T. Shimoda¹, Y. Wakabayashi³, Y. Gono², T. Suzuki¹, M. Ukai⁴, T. Wakui⁴, A. Yamazaki⁴, Y. Miyashita⁴, N. Sato⁴, M. Tateoka⁴, M. Ohguma⁴, T. Shinozuka⁴, T. Koike⁵, K. Shirotori⁵, Y. Miura⁵, S. Kinoshita⁵, Y. Ma⁵, Y. Y. Fu⁵ and H. Tamura⁵

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

Abstract

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 $\gamma \gamma$ 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 ( $\beta$ = - 0.17) of the $\ensuremath[\nu(f_{7/2}h_{9/2} i_{13/2}) \pi(h^4_{11/2})]_{61/2^+}$ 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 $\gamma$ transitions and level energies – / 27.70.+q 150 $\le$ A $\le$ 189 – / 29.30.Kv X- and $\gamma$ -ray spectroscopy –