J. A. Pinston

On the nature of the 17 μs isomer of the 133Sb valence nucleus

Abstract: The decay of the 17 μs isomer of 133Sb was re-investigated experimentally. It was produced by thermal neutron induced fission of 241Pu. Its detection is based on time correlation between fission fragments selected by the LOHENGRIN spectrometer at ILL (Grenoble), and the γ-rays, and conversion electrons from the isomer. The interpretation of the level scheme is based on shell model calculations, where empirical two-body matrix elements were employed. The good agreement between theory and experiment suggests that the isomer is the 21/2+ member of the 2p-1h πg7/2ν(f7/2h11/2−1) configuration.

High spin states in the transitional odd-odd nuclei150Eu and152Tb

The (7Li, 5n) and (11B, 5n) reactions have been used to study the high-spin states in the two odd-odd nuclei150Eu and152Tb. Three decoupled bands have been evidenced in each nucleus belonging to the same configurations [f7/2]n [h11/2]p, [h9/2]n [h11/2]p and [i13/2]n [h11/2]p. The latter one is well developped and improves our knowledge of this system between the spherical and deformed region. The analysis of the collective moment of inertia and transition ratios strongly suggests an increase of the deformation when the rotational frequency increases in these two transitional nuclei150Eu and152Tb.

19/2+ isomer of 125Cd and realistic shell-model calculations of neutron-rich Cd isotopes

The decay of a T1/2 = 19(3) μs isomeric state from 125Cd has been observed using γ-ray spectroscopy at the Lohengrin mass spectrometer of the Institut Laue-Langevin, Grenoble. Two coincident γ rays were observed to be emitted from the decay of this isomeric state, contradicting recently published data on this nucleus. Realistic shell-model calculations have been performed to interpret the decay scheme, allowing a spin and parity of 19/2+ to be assigned to the isomeric state. All configurations contributing to this isomeric state have amplitudes less than 7 %. Experimental data have recently been published on the decays of μs isomeric states in 127,128,130Cd. Realistic shell-model calculations for these nuclei are presented which reproduce the known experimental decay schemes reasonably well.

Medium-spin structure of Cs 145

Excited states in 145 Cs, populated following the spontaneous fission of 248 Cm, were studied by means of prompt-γ spectroscopy, using the EUROGAM2 multidetector array. A new level scheme of 145 Cs was proposed. We identified a decoupled band corresponding to 1/2 [550] proton configuration and interpreted the ground-state band as a mixed configuration of 1/2 [440] and 3/2 [422] proton orbitals. Quasiparticle-rotor calculations performed for 145 Cs support such assignments. The electric dipole moment in 145 Cs, Do = 0.013(4) efm, is smaller than in lighter Cs isotopes, which suggests that octupole correlations in Cs isotopes decrease at the neutron number N = 90, similarly as observed in the 146 Ba and 147 La isotones.

New information on excited states below the μs isomer in 136Sb

New experimental information has been obtained on the μs isomeric cascade in the very neutron-rich 136 Sb using γ-ray and conversion-electron spectroscopy at the Lohengrin mass spectrometer of the Institut Laue-Langevin. Two new transitions have been observed and their multipolarities determined, resolving the question of the origin of the isomerism. The new level scheme is in good agreement with predictions of a realistic shell-model calculation. The isomeric state is tentatively assigned a spin and parity of 6- and a proposed πg7/2 ν( f 7/2 ) 3 dominant configuration.

Near-yrast, medium-spin structure of {sup 143}Xe

Excited states in {sup 143}Xe, populated in spontaneous fission of {sup 248}Cm, are studied by means of {gamma} spectroscopy using the EUROGAM 2 Ge array. We identify three rotational bands in {sup 143}X: a decoupled band originating from the i{sub 13/2} neutron excitation, a strongly coupled band based on the 5/2{sup -} ground state, and a decoupled band based on the 322.9-keV level with spin 9/2. The new excitation scheme of {sup 143}Xe is compared to quasiparticle-rotor model calculations, performed with a reflection-symmetric potential.

Near-yrast structure of {sup 149}Pr

The neutron-rich nucleus

Two-quasiparticle isomers and bands of {sup 154,156}Nd and {sup 156,158,160}Sm

^{149}\mathrm{Pr}

Near-yrast structure of {sup 142}Cs and {sup 144}Cs

has been studied by means of prompt and delayed

The 11/2{sup -}[505] neutron extruder orbital in {sup 159}Sm

\ensuremath{\gamma}