Microscopic description of isobaric-analog-state transitions induced by 25-, 35-, and 45-MeV protons

Differential cross sections have been measured for ($p, n$) reactions to the isobaric analogs of the targets ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ at proton bombarding energies of 25, 35, and 45 MeV. The isospin-flip strength of a phenomenological nucleon-nucleon force has been determined with microscopic distorted-wave calculations including the "knock-on" exchange amplitude. A realistic $G$-matrix effective interaction also provides a reasonable account of the observed cross sections, particularly at the higher proton energies.