b-delayed proton decay of a high-spin isomer in 94Ag

The decay of the s7+d and s21+d isomers of the N=Z isotope 94Ag was studied at the GSI on-line mass separator by measuring b-delayed protons, g rays, proton-g and proton-g-g coincidences as well as the b-strength distribution. We have observed high-spin (up to 39/2) states in 93Rh populated by proton emission following the b decay of the 94Ag isomers. The major part of the population is related to the b decay of the known s7+d isomer whose half-life is 0.61s2d s. The assignment of the high-spin s21+d isomer in 94Ag with a half-life of 0.39s4d s has been confirmed. The excitation energy and b-decay energy of the s21+d isomer were measured to be at least 5.4 and 17.7 MeV, respectively. At this excitation energy, the s21+d isomer is expected to be unbound to direct one-proton, two-proton, or a decays. The remarkably long half-life of the s21+d isomer with the highest spin and excitation energy ever observed for b-decaying nuclei makes a new textbook example of a nuclear high-spin trap. The branching ratios for b-delayed proton emission are about 20% and 27% for the decays of the s7+d and s21+d isomers, respectively. The properties of the experimentally identified 93Rh levels are discussed in comparison to shell-model predictions.