Cross sections have been measured for the reaction ${}_{}{}^{64}{}_{}{}^{}\mathrm{Ni}$(n,p${)}^{64}$Co at laboratory angles between 0° and 10° for incident neutron energies from 90 to 240 MeV. The ground-state cross sections together with the ${\mathrm{\beta }}^{\mathrm{-}}$ decay ft value for the transition ${}_{}{}^{64}{}_{}{}^{}\mathrm{Co}$(g.s.)${\to }^{64}$Ni(g.s.) are used to normalize the q=0 differential cross section in units of mb/sr per unit Gamow-Teller (GT) strength. This is the first absolute measurement of the A(n,p) unit cross section for a nucleus in the (fp) shell, and it may be used to calibrate the GT strength measured in other (n,p) reactions of similar mass nuclei. Since the (${\mathit{e}}^{\mathrm{-}}$,${\nu }_{\mathit{e}}$) channel involves the same nuclear matrix element as the (n,p) channel, knowledge of GT strength in these nuclei is important for supernova modeling codes which depend on knowledge of ${\mathit{e}}^{\mathrm{-}}$ capture rates of (fp)-shell nuclei to determine parameters of stellar core collapse.

• Received 9 August 1991

DOI:https://doi.org/10.1103/PhysRevC.44.2794