EXCITATION-FUNCTIONS OF (P,ALPHA)-REACTIONS ON NI-64, KR-78, AND SR-86

Excitation functions were measured by the stacked-foil technique for N i-64(p,alpha)Co-61 and Sr-86(p,alpha)Rb-83 reactions from threshold up to 18.5 MeV. Thin samples of 95% enriched Ni-64 were prepared by elec trodeposition on gold foils, and those of 96.3% enriched (SrCO3)-Sr-86 via sedimentation on Cu backing. The radioactivity of the activation products was determined via high resolution gamma-ray spectrometry. St atistical model calculations taking into account preequilibrium effect s were performed for the experimentally measured competing reactions i nduced by protons on the target nuclei Ni-64, Kr-78, and Sr-86. The st rong (p, n) channel is described well by the calculation. In the case of weaker channels some discrepancies occurred between the experimenta l and theoretical data, in particular for Kr-78 as target. Regarding t he (p, alpha) process, an attempt was made to include direct three-nuc leon pickup component. For the neutron deficient target nuclei Kr-78 a nd Sr-86 the direct reaction contribution to the (p,alpha) cross secti on appears to be small, presumably due to large (p, n) thresholds. Inc lusion of this component in the (p,alpha) reaction on the neutron rich target nuclide Ni-64, however, led to a better agreement between the experimental and theoretical data.