Quasielastic (p, n) reactions were studied at an incident proton energy of 35 MeV. Differential cross sections for isobaric analog $\Delta J^{\pi }{=0\mathrm{}}^{+}$ (Fermi-type) transitions and their angular distributions were measured in 27 $N>Z$ target nuclei ${}^7\mathrm{Li},$ ${}^9\mathrm{Be},$ ${}^{13,14}\mathrm{C},$ ${}^{15}\mathrm{N},$ ${}^{50}\mathrm{Cr},$ ${}^{54,56}\mathrm{Fe},$ ${}^{58,60,62,64}\mathrm{Ni},$ ${}^{70}\mathrm{Zn},$ ${}^{71}\mathrm{Ga},$ ${}^{92}\mathrm{Zr},$ ${}^{110,112,114,115}\mathrm{Cd},$ ${}^{116,118,120}\mathrm{Sn},$ ${}^{140}\mathrm{Ce},$ ${}^{172,174,176}\mathrm{Yb},$ and ${}^{208}\mathrm{Pb}.$ Pure $\Delta J^{\pi }{=0\mathrm{}}^{+}$ Fermi-type transitions were observed in 23 of them. As for the four light odd-A nuclei, contributions from mixed $\Delta J^{\pi }\ne 0^{+}$ components 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 27 $\Delta J^{\pi }{=0\mathrm{}}^{+}$ angular distributions were obtained, and fitted by macroscopic DWBA calculations with the Lane-model optical potential to derive systematically the isovector part of the potential. The best-fit parameters for each target are presented. The present results combined with our previous analysis on 13 other nuclei in the $17<~A<~48$ region cover almost the entire mass region. They were used to obtain A-dependent global parameters by least-squares fit.

• Received 2 November 1999

DOI:https://doi.org/10.1103/PhysRevC.62.044609