Spin-isospin strength distributions in f-p shell nuclei: A study of the 51V(n,p) and 59Co(n,p) reactions at 198 MeV.

Abstract

The (n,p) reaction has been studied on the nuclei $^{51}\mathrm{V}$ and $^{59}\mathrm{Co}$ at an energy of 198 MeV. Spectra were measured at laboratory angles of 0\ifmmode^\circ\else\textdegree\fi{}, 4\ifmmode^\circ\else\textdegree\fi{}, 8\ifmmode^\circ\else\textdegree\fi{}, 12\ifmmode^\circ\else\textdegree\fi{}, 16\ifmmode^\circ\else\textdegree\fi{}, and 20\ifmmode^\circ\else\textdegree\fi{} up to an excitation energy of 35 MeV in the final nuclei $^{51}\mathrm{Ti}$ and $^{59}\mathrm{Fe}$. A multipole analysis of the data up to 30 MeV was carried out to identify Gamow-Teller (\ensuremath{\Delta}L=0,\ensuremath{\Delta}${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${1}^{+}$) and spin dipole (\ensuremath{\Delta}L=1,\ensuremath{\Delta}${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${0}^{\mathrm{\ensuremath{-}}}$,${1}^{\mathrm{\ensuremath{-}}}$,${2}^{\mathrm{\ensuremath{-}}}$) strengths. GT strength is concentrated in a resonance with centroid energy of 5.2 MeV in $^{51}\mathrm{Ti}$ and 4.1 MeV in $^{59}\mathrm{Fe}$. The spin-dipole strength appears as a broad resonance with centroid energy about 16 MeV in both nuclei. Shell model calculations of the GT strength reproduce the energy distribution reasonably well, but the calculated strength exceeds the measurement by a factor of about four.