(p,n) Cross Sections and the Strength Functions for 3- to 5.5-MeV Protons on In and on Sn Isotopes

Abstract

The ($p,n$) reaction cross sections were measured to ±4% for 3- to 5.5-MeV protons on ${}_{}{}^{117,119,120,122,124}{}_{}{}^{}\mathrm{Sn}$ and on natural Sn and In. Analyses with a conventional optical-model potential were made in the energy regions where the ($p,n$) cross sections are nearly equal to the total absorption cross sections. These analyses show that the energv dependence in the real well is about three times greater for 5- to 10-MeV protons than it is for 10- to 61-MeV protons. The best-fit potential for 3- to 5.5-MeV protons on the Sn isotopes has a surface absorptive layer about half as thick as at 10 MeV. The In strength functions are fitted by increasing both the width and depth of the imaginary part of this potential by about 25%. The $Q$ value for ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}\mathrm{}(p,n)\mathrm{}{}_{}{}^{120}{}_{}{}^{}\mathrm{Sb}$ was found to be -3465 ± 7 keV.