β−-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes

Abstract

The low-lying structure of W188,190,192 has been studied following β decays of the neutron-rich mother nuclei Ta188,190,192 produced following the projectile fragmentation of a 1-GeV-per-nucleon Pb208 primary beam on a natural beryllium target at the GSI Fragment Separator. The β-decay half-lives of Ta188, Ta190, and Ta192 have been measured, with γ-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion β−γ correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in W188, W190, and W192, which highlight a change in nuclear shape at W190 compared with that of lighter W isotopes. This evolution of ground-state structure along the W isotopic chain is discussed as evidence for a possible proton subshell effect for the A~ 190 region and is consistent with maximization of the γ-softness of the nuclear potential around N~116.11 MoreReceived 18 September 2009DOI:https://doi.org/10.1103/PhysRevC.80.064308©2009 American Physical Society