12C(n,p)12B reaction at 56, 60, and 65 MeV.

Abstract

The {sup 12}C({ital n},{ital p}){sup 12}B reaction has been studied at 60 and 65 MeV. Cross sections for the 1{sup +} ground state, the 2{sup +} first excited state at 0.95 MeV, an unresolved pair of 2{sup {minus}} and 4{sup {minus}} states at 4.4 MeV, and the analogs of the giant electric dipole and spin-dipole resonances around 7.7 MeV have been extracted and compared with previous data at 56 MeV and with microscopic distorted-wave Born approximation calculations. The shapes of angular distributions out to {ital q}{similar to}2 fm{sup {minus}1} are well reproduced by the calculations. A comparison of ({ital n},{ital p}), ({ital p},{ital n}), and ({ital p},{ital p}{prime}) cross sections near 60 MeV is made, and a value for {vert bar}{ital J}{sub {sigma}{tau}}{vert bar} (the volume integral of the central, spin-isospin part of the effective nucleon-nucleon interaction) is extracted. The magnitudes of cross sections for negative-parity states can be qualitatively understood when the loose binding of the {ital sd}-shell neutron in the final state and the effect of ground-state correlations on the dipole and spin-dipole strengths are taken into account.