Decay of a πh11/2νh11/2 microsecond isomer in 61136Pm75

S. V. Rigby, D. M. Cullen, P. J. R. Mason, D. T. Scholes, C. Scholey, P. Rahkila, S. Eeckhaudt, T. Grahn, P. Greenlees, P. M. Jones, R. Julin, S. Juutinen, H. Kettunen, M. Leino, A.-P. Leppänen, P. Nieminen, M. Nyman, J. Pakarinen, and J. Uusitalo
Phys. Rev. C 78, 034304 – Published 3 September 2008

Abstract

An experiment has been performed to populate several extremely neutron-deficient nuclei around the mass-140 region of the nuclear chart, using a beam of Fe54 on a Mo92 target at an energy of 315 MeV. Analysis of these data using recoil-isomer tagging has established that the yrast πh11/2νh11/2,Jπ=(8+), bandhead state in Pm136 is isomeric with a half-life of 1.5(1) μs. This isomeric state decays via a 43-keV, probable-E1 transition to a Jπ=(7) state. Consideration of the theoretical Nilsson orbitals near the Fermi surface suggests that the Jπ=(8+) state has a νh11/2[505]112πh11/2[532]52 configuration, which decays to the Jπ=(7) state with a νh11/2[505]112πd5/2[411]32+ configuration. Differences in the shape-driving effects for these two configurations is reasoned to be responsible for the long half-life of the Jπ=(8+) isomeric state. The non-observation of other γ rays in prompt or delayed coincidence with the 43-keV transition suggests that this transition may feed another, longer lived isomeric state with a half-life of the order of milliseconds or greater. However, the present experiment was not sensitive to the decay of this new Jπ=(7) state by internal conversion or even β decay.

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  • Received 8 May 2007

DOI:https://doi.org/10.1103/PhysRevC.78.034304

©2008 American Physical Society

Authors & Affiliations

S. V. Rigby1, D. M. Cullen1, P. J. R. Mason1, D. T. Scholes1, C. Scholey2, P. Rahkila2, S. Eeckhaudt2, T. Grahn2,*, P. Greenlees2, P. M. Jones2, R. Julin2, S. Juutinen2, H. Kettunen2, M. Leino2, A.-P. Leppänen2, P. Nieminen2,†, M. Nyman2, J. Pakarinen2,*, and J. Uusitalo2

  • 1Schuster Laboratory, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, United Kingdom
  • 2Department of Physics, University of Jyväskylä, Jyväskylä, FIN-40014, Finland

  • *Present address: Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 3BX, United Kingdom.
  • Present address: Department of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.

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Vol. 78, Iss. 3 — September 2008

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