Polarization of Neutrons and Protons by Scattering

Neutrons and protons can be polarized by scattering provided there is a spin-orbit interaction between the incident particle and the scattering nucleus. The polarization effect has been found for a nucleus of spin zero allowing for the possibility of resonance scattering. Particular attention has been paid to the resonance scattering of neutrons by He⁴ where almost full polarizations can be obtained, together with large cross sections. The polarization can be detected by a double scattering experiment, since the second scattering will be axially asymmetric with respect to the direction of the first scattered neutron. The existence of this effect and a preliminary treatment of it was first pointed out by Schwinger.The scattering of polarized neutrons by protons has been studied for potentials suggested by the symmetrical, charged and neutral meson theories. The polarization effect on the differential cross section is negligible for the symmetrical theory, but is significant for the other two.