Polarization Effects following Beta Decay

With a view to providing alternative methods of determining the dominant invariants in the beta interaction, various polarization effects following the beta decay of unoriented nuclei are discussed. In both $K$ capture and beta emission the recoiling nucleus is polarized along its line of flight. Measurement of this polarization could determine whether the tensor or axial vector interaction is dominant. The hole in the $K$ shell following $K$ capture is also polarized relative to the recoil direction. Measurement of the hole polarization can distinguish between the scalar and vector as well as between the tensor and axial vector interactions. Methods for detecting the polarizations are discussed. The longitudinal polarization of the recoiling nucleus can in principle be detected directly by atomic beam techniques or indirectly by measuring the correlation between the direction of the recoiling nucleus and the direction and circular polarization of a subsequent radiation (gamma ray, conversion electron, or beta particle). The polarization of the hole in the $K$ shell following $K$ capture can perhaps be determined by a recoil-x-ray circular polarization correlation experiment.