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Gamow-Teller transition probabilities are extracted for eight nuclei with masses between 3 = 13 and 39 from medium-energy (p, n) reactions via the distorted-wave impulse approximation, and compared with experimental P-decay and with free-nucleon transition probabilities. These comparisons indicate strongly that the renormalization of the Gamow-Teller operator needed for (p, n) reactions on finite nuclei is different from that needed for P decay.

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Background: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 58,60,62,64 Ni(p, n) 58,60,62,64 Cu reactions were measured over the angular range of 0.3 • to 11.6 • at 134.3 MeV using the IUCF neutron time-of-flight facility. Results: The T o + 1 excitations in 60,62 Ni 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.