Jirina Stone

Abstract:

The [Formula Presented]/EC decay of mass-separated [Formula Presented] nuclei was studied by means of [Formula Presented]- and [Formula Presented]-ray spectroscopy after the bombardment of a [Formula Presented] Mg target with [Formula Presented] Ni ions at 190 MeV. A new 1[Formula Presented] isomer at 228.5(1) keV has been identified in [Formula Presented] Y with a half-life of 4.7(3) s. This new isomer decays to the 4[Formula Presented] ground state with an 81(2)[Formula Presented] branch and by [Formula Presented]/EC transitions to levels in [Formula Presented] Sr with a 19(2)[Formula Presented] branch. The half-life of the [Formula Presented] Y ground-state decay has been remeasured to be 30.1(5) s. A level scheme for the low-lying states in [Formula Presented] Y is presented. Hartree-Fock-Bogolyubov calculations show a large prolate deformation for these states, and two-quasiparticle + rotor model calculation results suggest that the low-lying states can be reproduced by inclusion of an effective proton-neutron residual interaction. The dominating Nilsson configurations for the 4[Formula Presented] ground state and the 1[Formula Presented] isomeric state have been found to originate from the parallel and antiparallel coupling of the proton [422]5/2[Formula Presented] and the neutron [301]3/2[Formula Presented] orbitals. © 1998 The American Physical Society.