The spin-orbit interaction in the scattering of 147–220 MeV nucleons by light nuclei

Abstract

The polarizations and differential cross sections in the elastic scattering of 147–220 MeV nucleons by He 4, Li 7, C 12 and Al 27 are examined using the optical model. The usual form of the nuclear potential. ν(r) = −(V+iW)g(r)+(γ+iδ)r −( dg dr ) σ· L , where g( r) is a Woods-Saxon form factor, is found to be inadequate for a detailed description of the observations especially for light nuclei. Taking a spin-orbit potential of the form γ′+iδ′){r −3( d 2g dr 2 )+ε′r −( dg dr )} σ· L gives substantially better agreement with the data. It is shown how this modification of the Thomas-Fermi spin-orbit interaction may be related to higher order terms in the optical model expansion obtained in Born approximation from nucleon-nucleon scattering amplitudes.