First decay study of the very neutron-rich isotope Br-93

The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes.Comment: 17 pages, 3 figures, Phys. Rev. C, in prin

Identical transitions in the strongly deformed Sr-99 and Sr-100

The decay of the very neutron-rich nucleus Rb-100 has been studied by gamma-spectroscopy of on-line mass-separated samples. Schemes for beta-decay to Sr-100 and beta-n-decay to Sr-99 are presented. New sets of transitions in Sr-99 and Sr-100 with identical energies are observed. All identical bands so far observed in neutron-rich Sr isotopes obey a simple energy rule valid for even-even, odd-even and odd-odd bands.Comment: 31 pages, 7 figures, Phys. Rev. C, in prin

Levels in 99Zr observed in the decay of 99Y

New investigation of the decay scheme of 99Y to 99Zr removes minor discrepancies between decay and prompt-fission data.The existence of a strongly coupled band on the 725-keV level postulated in an earlier beta-decay work is not confirmed. Calculations in the IBFM framework allow an alternative interpretation of the even-parity levels above 500 keV

A tentative 4- isomeric state in Sr-98

Annual Report 2001, Institut fuer Kernchemie, Johannes-Gutenberg-Universitaet, Mainz, GermanyComment: 3 pages, 1 figur

First decay study of the very neutron-rich isotope Br-93

The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes.The decay of the mass-separated, very neutron-rich isotope Br-93 has been studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been constructed. Level energies, gamma-ray branching ratios and multipolarities suggest spins and parities which are in accord with a smooth systematics of the N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to be effective in Kr isotopes. So far, there is no indication of a progressive onset of deformation in neutron-rich Kr isotopes

Shape coexistence in the odd-odd neutron-rich nucleus 98Y studied in the interacting boson model

Data on levels in 98Y have been investigated and interpreted using recently published information on band structure in this region. Calculation in the IBM framework suggests that the 1182 keV isomer is spherical 10- state with π g9/2 ν h11/2 configuration. This assignment implies that the 8.0 microsecond bandhead at 496 keV is a 4- state with highly probable π(422)5/2 ν(541)3/2 configuration. The level structure of 98Y is well reproduced by coupling the levels of its both spherical and deformed odd-A neighbors and the origin of the isomeric states is understood

Nuclear structure of 97Y in the interacting boson fermion plus broken pair model and the nature of the 3.523 MeV high-spin isomer

Nuclear structure of 97Y is described in the interacting boson fermion plus broken pair model, including quasiproton and quasiproton-two-quasineutron configurations in the basis states. In particular, the yrast bands and the decay of the 27/2- high-spin isomer are accounted for in this approach

Application of realistic effective interactions to the structure of the Zr isotopes

We calculate the low-lying spectra of the zirconium isotopes Z=40 with neutron numbers from N=52 to N=60 using the 1p1/20g9/2 proton and 2s1d0g7/20h11/2 neutron sub-shells to define the model space. Effective proton-proton, neutron--neutron and proton-neutron interactions have been derived using 88Sr as closed core and employing perturbative many-body techniques. The starting point is the nucleon-nucleon potential derived from modern meson exchange models. The comprehensive shell-model calculation performed in this work provides a qualitative reproduction of essential properties such as the sub-shell closures in 96Zr and 98Zr.Comment: To appear in Phys Rev C, june 2000, 8 figs, Revtex latex styl

Level structure of ^100Nb

Levels in the odd-odd nucleus ^100Nb situated at the edge of a region of especially fast shape transitions have been calculated in the framework of the interacting boson fermion fermion model. Levels observed in decay studies can be interpreted in a spherical basis. Low-lying I^π=8^+ and 10^- states are predicted. Their relationship with the unplaced levels populated with a 12 μs delay after fission is discussed