β-delayed proton decay of a high-spin isomer inA94g

Abstract

The decay of the (7{sup +}) and (21{sup +}) isomers of the N=Z isotope {sup 94}Ag was studied at the GSI on-line mass separator by measuring {beta}-delayed protons, {gamma} rays, proton-{gamma} and proton-{gamma}-{gamma} coincidences as well as the {beta}-strength distribution. We have observed high-spin (up to 39/2) states in {sup 93}Rh populated by proton emission following the {beta} decay of the {sup 94}Ag isomers. The major part of the population is related to the {beta} decay of the known (7{sup +}) isomer whose half-life is 0.61(2) s. The assignment of the high-spin (21{sup +}) isomer in {sup 94}Ag with a half-life of 0.39(4) s has been confirmed. The excitation energy and {beta}-decay energy of the (21{sup +}) isomer were measured to be at least 5.4 and 17.7 MeV, respectively. At this excitation energy, the (21{sup +}) isomer is expected to be unbound to direct one-proton, two-proton, or {alpha} decays. The remarkably long half-life of the (21{sup +}) isomer with the highest spin and excitation energy ever observed for {beta}-decaying nuclei makes a new textbook example of a nuclear high-spin trap. The branching ratios for {beta}-delayed proton emission are about 20% and 27% for the decays of the (7{sup +}) andmore » (21{sup +}) isomers, respectively. The properties of the experimentally identified {sup 93}Rh levels are discussed in comparison to shell-model predictions.« less