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 πh11/2?νh11/2, 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]112-? πh11/2[532]52- configuration, which decays to the Jπ=(7-) state with a νh11/2[505]112-?πd5/2[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.
| Original language | English |
|---|---|
| Article number | 034304 |
| Journal | Physical Review C - Nuclear Physics |
| Volume | 78 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 3 Sept 2008 |
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