Interaction of 80-164 MeV protons with nickel isotopes

Production cross sections of various final nuclei have been determined using the in-beam gamma rays produced during the 80, 100, 136, and 164 MeV proton bombardment of ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$, ${}_{}{}^{62}{}_{}{}^{}\mathrm{Ni}$, and ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$ targets. From the systematics of these cross sections it is concluded that (a) typically, 1-2 nucleons are emitted in the fast pre-equilibrium phase leaving a few nuclei excited over a broad range of excitation energy, (b) the bulk of the final nuclei are produced following nucleon evaporation from the excited nuclear residues of the pre-equilibrium phase, (c) the fraction of the incident energy dissipated through fast emission increases from about $\frac{1}{2}$ to $\frac{2}{3}$ over the above energy range, (d) the average excitation energy of the nuclear residues of the pre-equilibrium phase is estimated to increase by only 10 MeV in going from about 40 to 50 MeV over the above energy range, and (e) no evidence is found for significantly preferred removal of alpha particles from the target nucleus. Detailed comparisons of the observed cross sections are made with the cascade and hybrid models. The cascade model yields better overall agreement with the measured results. A hybrid model which includes both multiple pre-equilibrium emission and geometric surface effects is needed if it is to be equally effective.