Imaginary Optical Potential for the Compound NucleusPb209

A nonlocal energy-dependent imaginary optical potential for $s$-wave neutrons incident on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ is calculated in the intermediate structure model with particle-vibration coupling. The energy dependence is studied in the range of 0-12 MeV. The absorption cross section is calculated and compared to experiment below 2.6 MeV, the inelastic threshold. The agreement is quite good. The radial dependence is also investigated.