Journal Club: Metastable States of 92,94Se: Identification of an Oblate K Isomer of 94Se and the Ground-State Shape Transition between N=58 and 60
焦长峰
10月31日晚上19:30-21:00
天琴大楼2316
Metastable States of 92,94Se: Identification of an Oblate K Isomer of 94Se and the Ground-State Shape Transition between N=58 and 60
Here we present new information on the shape evolution of the very neutron-rich 92,94Se nuclei from an isomer-decay spectroscopy experiment at the Radioactive Isotope Beam Factory at RIKEN. High-resolution germanium detectors were used to identify delayed γ rays emitted following the decay of their isomers. New transitions are reported extending the previously known level schemes. The isomeric levels are interpreted as originating from high-K quasineutron states with an oblate deformation of β∼0.25 , with the high-K state in 94Se being metastable and K hindered. Following this, 94Se is the lowest-mass neutron-rich nucleus known to date with such a substantial K hindrance. Furthermore, it is the first observation of an oblate K isomer in a deformed nucleus. This opens up the possibility for a new region of K isomers at low Z and at oblate deformation, involving the same neutron orbitals as the prolate orbitals within the classic Z ∼72 deformed hafnium region. From an interpretation of the level scheme guided by theoretical calculations, an oblate deformation is also suggested for the 94Se60 ground-state band.