Gamow-Teller and dipole strength distribution in 40Ca(n,p)40K reaction.

Abstract

Double differential cross-section angular distributions covering 0\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}${\mathrm{\ensuremath{\theta}}}_{\mathrm{lab}}$\ensuremath{\le}40\ifmmode^\circ\else\textdegree\fi{} have been measured for the $^{40}\mathrm{Ca}$(n,p${)}^{40}$K charge exchange reaction. With the white neutron source at LAMPF-WNR, we were able to study not only the angular distribution but also the energy dependence of this charge exchange reaction covering simultaneously incident neutron energies between 60 and 260 MeV. The identification of Gamow-Teller (GT) transitions and L=1 dipole resonance was carried out using a multipole decomposition technique. The empirically deduced GT strength in the $^{40}\mathrm{Ca}$(n,p${)}^{40}$K reaction evaluated up to 15 MeV excitation energy is compared to theoretical values. We have used a simple one-particle--one-hole shell model calculation to study the excitation of the giant dipole resonance and the giant spin-dipole resonance, which are compared with empirical results.