Jirina Stone

Abstract:

The odd-odd [Formula Presented] nuclide, [Formula Presented] has been produced in the [Formula Presented] reaction at 125 MeV. Recoiling fragments separated by their [Formula Presented] values were implanted onto the tape of a moving tape collector and transported to a shielded position between two plastic β detectors and two Ge γ-ray detectors where β-γ coincidences were recorded as a function of time. γ rays with energies of 279 (100%), 504 (90%), and 713 (40%) keV, previously identified as yrast transitions in daughter [Formula Presented] were observed and found to decay with a half-life of 5.8 (6) s. From the relative intensities of the γ-rays, a spin and parity of [Formula Presented] and [Formula Presented] are assigned to the parent state in [Formula Presented] undergoing β decay. A production cross section of [Formula Presented] has been determined for [Formula Presented] by comparison of the counting rates with those of other reaction products with known cross sections. An upper limit of 500 keV can be set for the energy of this level relative to a possible highly deformed [Formula Presented] ground state. From this limit, it can be inferred that [Formula Presented] pairing is considerably quenched relative to such pairing in adjacent odd-odd [Formula Presented] Two-quasiparticle rotor model calculations have been used to account for the structure of [Formula Presented] and adjacent nuclides. © 1998 The American Physical Society.

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.