Electron capture strength for 60,62Ni and 58,60,62,64Ni(p, n)58,60,62,64Cu reactions at 134.3 MeV

The strength of electron capture for medium mass nuclei has a significant effect on the evolution of supernovae. There is insufficient knowledge of these strengths and very little data for important radioactive nuclei. Purpose: Determine whether it is feasible to obtain EC strength from studies of T-o + 1 excitations in (p, n) reactions, and whether this might yield information for radioactive nuclei. Methods: Cross sections for the Ni-58,Ni-60,Ni-62,Ni-64(p, n)Cu-58,Cu-60,Cu-62,Cu-64 reactions were measured over the angular range of 0.3 degrees to 11.6 degrees at 134.3 MeV using the IUCF neutron time-of-flight facility. Results: The T-o + 1 excitations in Ni-60,Ni-62 were identified by comparison with inelastic proton scattering spectra, their B(GT) were extracted, and the corresponding electron capture rates in supernovae were calculated. Data from the TRIUMF (n, p) experiments at 198 MeV were reanalyzed; the electron capture rates for the reanalyzed data are in moderately good agreement with the higher resolution (p, n) results, but differ in detail. The possibility of future measurements with radioactive nuclei was considered. Conclusions: It may be possible to obtain low-lying electron capture strength for radioactive nuclei by studying (p, n) reactions in inverse kinematics.