High-resolution determination of GT strength distributions relevant to the presupernova evolution using the (<f>d</f>,2He) reaction

Spin–isospin excitations of the medium-mass nucleus 58Co were studied using the <f>(n,p)</f>-type <f>(d,2He)</f> charge-exchange reaction at an incident energy <f>Ed=170</f> MeV and small scattering angles. The achieved energy resolution of 130 keV, full width at half maximum, allowed the extraction of Gamow–Teller strength to 13 peaks at excitation energies lower than 4.1 MeV in the residual nucleus 58Co and is consistent with the results of a multipole-decomposition analysis. The identification of Gamow–Teller transitions is possible by comparison of the measured cross sections with DWBA calculations. The results are used to discuss the relevance of the Gamow–Teller strength distribution at low excitation energy with regard to electron-capture rates used in calculations for the final stage of a massive star. [Copyright &y& Elsevier]