Proton decay from the isoscalar giant dipole resonance in ^{58}Ni

Proton decay from the 3 (h) over bar omega isoscalar giant dipole resonance (ISGDR) in Ni-58 has been measured using the (alpha, 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 alpha particles at forward angles and decay protons emitted at backward angles. Branching ratios for proton decay to low-lying states of Co-57 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 Co-57 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.