Structure of isobaric analog states in 91Nb populated by the 90Zr(a,t) reaction

Decay via proton emission of isobaric analog states (IAS’s) in ${}^{91}Nb$ was studied using the ${}^{90}Zr(\alpha ,t)$ reaction at $E_{\alpha }$=180 MeV. This study provides information about the damping mechanism of these states. Decay to the ground state and low-lying phonon states in ${}^{90}Zr$ was observed. The experimental data are compared with theoretical predictions wherein the IAS `single-particle’ proton escape widths are calculated in a continuum RPA approach. The branching ratios for decay to the phonon states are explained using a simple model.