Isobaric Analog Resonances in theZn68(p, n)Ga68Reaction from 4 to 5 MeV

Two pairs of isobaric analog resonances near 4.1- and 4.9-MeV proton bombarding energy, respectively, have been studied in the ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}(p, n){}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ reaction. Differential cross sections were measured at 2.5, 30, and 130° for neutrons which leave ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ in the ground state and 180-keV first excited state in the bombarding energy region from 4.00 to 4.15 MeV. Analog resonances at 4.075 and 4.098 MeV were analyzed according to the Robson theory. Eleven levels in ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ up to an excitation energy of 1.088 MeV were identified in time-of-flight spectra. Hauser-Feshbach analyses were done on the angular distributions of neutrons leaving ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$ in 4 and 6 residual nucleus states at 4.400 and 4.512 MeV, respectively, an energy region where no analog resonances appear. Excitation functions for seven neutron groups were measured at 100° in the bombarding energy region 4.7 to 5.0 MeV, where two analog resonances, at 4.87 and 4.92 MeV, were seen. An analysis according to the theory of Robson was performed on these resonances in order to obtain spins, parities, and resonance parameters.