New and comprehensive beta- and beta p-decay spectroscopy results in the vicinity of Sn-100

Abstract

A decay spectroscopy experiment on proton-rich nuclei in the vicinity of the doubly magic Sn-100 was carried out at RIKEN Nishina Center. More than 20 nuclei with 43 <= Z <= 50 and N <= 51, produced by fragmentation reactions were investigated via analyses of beta-decay, beta p-decay, and subsequent gamma-ray data. Owing to higher statistics, the precision on the half-lives of many of the ground states and isomers was improved. beta-decay endpoint energies of 11 states in 8 nuclei were measured for the first time, and the corresponding Q(EC) and excitation energies were generally consistent with various mass models. Many beta-delayed proton emission branching ratios were measured either for the first time or with higher precision compared to literature values, and some of them differed by more than 2 sigma. Many of the large discrepancies were associated with nuclei with long-lived isomeric states, highlighting large systematic uncertainties involved in these measurements. Twenty-five new gamma rays were observed, and ten new states are proposed with unambiguous excitation energies, spins, and parities. Most of the energies of the excited states were consistent within 300 keV or 20%, whichever was greater, compared to shell model predictions in the proton/neutron (P-1/2, g(9/2)) model space assuming a Sr-76 core. A signature of a new (1/2(-)) isomer in Cd-97 with T-1/2 = 0.73(7) s was found, in good agreement with shell model predictions.