Proton Strength Functions for Sn and the Optical Model Below the Coulomb Barrier

Abstract

Proton strength functions were determined from the ($p, n$) reactions for 3- to 5.5-MeV protons on ${}_{}{}^{117,119,120,122,124}{}_{}{}^{}\mathrm{Sn}$. The $3p$ size resonance was found. Optical-model analyses show that the energy dependence in the real well is 3 times greater for 5- to 10- MeV protons than for 10- to 16-MeV protons. The best fit potential for 3- to-5.5 MeV protons has a surface absorptive layer about half as thick as at 10 MeV.