Complex spin-orbit potential forPb208(n, n)Pb208at 10 MeV

The analyzing power $A_y\left(\theta \right)$ and differential cross section $\sigma \left(\theta \right)$ have been measured for elastic scattering of 10-MeV neutrons from ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. These data were analyzed with a spherical optical model which has a real spin-orbit potential with either a three-parameter conventional form or a one-parameter semimicroscopic form. The predictions with both spin-orbit potentials reproduce the data equally well, suggesting that fewer free parameters can be used in spherical optical model calculations. Including an imaginary spin-orbit term $W_{\mathrm{SO}}\mathrm{}\left(r\right)\mathrm{}$ in the optical potential greatly improves the fits to the $A_y\left(\theta \right)$ measurements and establishes the need for $W_{\mathrm{SO}}\mathrm{}\left(r\right)\mathrm{}\ne 0$ in the n + ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ potential.