Analog transitions insd- andf-shell nuclei and the isovector part of optical potentials studied by the(p,n)reaction at 35 MeV

Abstract

Quasielastic $(p,n)$ reactions on $\mathrm{sd}$- and $f$-shell nuclei were studied at an incident proton energy of 35 MeV. Differential cross sections for isobaric analog $\ensuremath{\Delta}{J}^{\ensuremath{\pi}}{=0}^{+}$ (Fermi-type) transitions and their angular distributions were measured in 13 $NgZ$ target nuclei ranging $17l~Al~48,$ ${}^{17,18}\mathrm{O},$ ${}^{22}\mathrm{Ne},$ ${}^{25,26}\mathrm{Mg},$ ${}^{27}\mathrm{Al},$ ${}^{30}\mathrm{Si},$ ${}^{34}\mathrm{S},$ ${}^{38,40}\mathrm{Ar},$ and ${}^{42,44,48}\mathrm{Ca}.$ Pure $\ensuremath{\Delta}{J}^{\ensuremath{\pi}}{=0}^{+}$ Fermi-type transitions were observed in six of them. As for the other seven nuclei, contributions from mixed $\ensuremath{\Delta}{J}^{\ensuremath{\pi}}\ensuremath{\ne}{0}^{+}$ components or those from unresolved transitions were evaluated by microscopic distorted-wave Born approximation (DWBA) calculations to subtract them from the raw data and extract pure Fermi-type transition strengths. Thus a total of 13 $\ensuremath{\Delta}{J}^{\ensuremath{\pi}}{=0}^{+}$ angular distributions was fitted by macroscopic DWBA calculations with a Lane-model optical potential to derive systematically the isovector part of the potential. The best-fit parameters for each target are presented. $A$-dependent global parameters were obtained from these best-fit parameters by a least-squares fit.