Proton decay from the isoscalar giant dipole resonance inNi58

Abstract

Proton decay from the $3\ensuremath{\hbar}\ensuremath{\omega}$ isoscalar giant dipole resonance (ISGDR) in $^{58}\mathrm{Ni}$ has been measured using the ($\ensuremath{\alpha},{\ensuremath{\alpha}}^{'}p$) reaction at a bombarding energy of 386 MeV to investigate its decay properties. We have extracted the ISGDR strength under the coincidence condition between inelastically scattered $\ensuremath{\alpha}$ particles at forward angles and decay protons emitted at backward angles. Branching ratios for proton decay to low-lying states of $^{57}\mathrm{Co}$ have been determined, and the results compared with predictions of recent continuum-RPA calculations. The final-state spectra of protons decaying to the low-lying states in $^{57}\mathrm{Co}$ were analyzed for a more detailed understanding of the structure of the ISGDR. It is found that there are differences in the structure of the ISGDR as a function of excitation energy.