Author:

Keywords:

Energy, nuclear shell-model, neutron-rich nuclei, 70Ni,72Ni,74Ni, ni isotopes, spectroscopy, beta-decay, sn-100, identification, magicity, states, isomer, Science & Technology, Physical Sciences, Physics, Nuclear, Physics, NUCLEAR SHELL-MODEL, NEUTRON-RICH NUCLEI, NI ISOTOPES, BETA-DECAY, SN-100, IDENTIFICATION, MAGICITY, STATES, ISOMER, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics, 5106 Nuclear and plasma physics

Abstract:

The yrast J(pi)=8(+) states in neutron-rich Ni-70,Ni-72,Ni-74,Ni-76 nuclei are predicted to be isomeric. The present paper describes two GANIL experiments. In the first of them a search was made for the 8(+) isomeric states in Ni-72,Ni-74 nuclei via fragmentation of Ge-76 using the ion gamma-decay correlation technique. Although these states were not observed, limits for their lifetimes were determined. In the second experiment the decay spectroscopy of Co-70,Co-72 nuclei was performed using fragmentation of a Kr-86(36+) beam and the new LISE2000 spectrometer. The beta delayed gamma rays from the decay of Co-70,Co-72 to Ni-70,Ni-72 were observed using the EXOGAM germanium detectors. The half life of Co-72 was measured to be 62(3) ms and the level sequence of the lowest excited states in Ni-72 was suggested, with the 2(+) state at 1096 keV. An attempt to reproduce the level scheme in terms of shell-model calculations was undertaken. The reasons for the disappearance of the 8(+) isomer in Ni-72 are discussed.