Nonlocal Optical-Model Analysis of Neutron Scattering from Nuclei NearA=100at Energies Below 1 MeV

The polarization and differential cross sections for neutrons scattered from the nuclei Zr, Nb, Mo, and Cd have been measured at five angles for neutron energies between 0.275 and 0.85 MeV. The results have been analyzed in terms of an optical model equivalent to the nonlocal model of Perey and Buck. The analysis leads to the following conclusions: (1) The calculations, corrected for the effects of compound elastic scattering, are consistent with most of the scattering data when a spin-orbit potential that includes both a real ($V_S\approx 10$ MeV) and an imaginary ($W_S\approx 4$ MeV) term of the Thomas type is employed. (2) As calculated on the basis of this model, the magnitude and shape of the $P$-wave neutron strength-function peak in the region near $A=100\mathrm{}$ are rather insensitive to the values chosen for the real and imaginary spin-orbit potentials—at least for $7.2<~V_S<~20$ MeV and $0<~W_S<~7.2$ MeV. Thus, on the basis of this model the possible splitting of the $3P$ strength function peak cannot be interpreted in terms of a spin-orbit force.