Parity-Nonconserving Internucleon Potentials. II. Effects in Electromagnetic Transitions

Abstract

A detailed investigation is made of the way in which parity-nonconserving (PNC) internucleon potentials lead to parity impurities in nuclear states and hence to pseudoscalar asymmetries in the emission of gamma radiation. Explicit expressions are obtained for the angular distribution of unpolarized radiation (a) in emission from nuclei polarized by non-nuclear methods, (b) in $\beta -\gamma$ angular correlations, (c) in polarized thermal neutron capture radiation and also for the magnitude of the circular polarization of radiation from an arbitrarily oriented nuclear system. The magnitudes of these effects are then estimated for the case of a transition between low-lying nuclear states and also for a ground-state transition following neutron capture. Finally a critique of the $\gamma$-ray transitions so far used in experimental investigations of PNC effects is given. It is concluded that many transitions in particularly simple nuclei are insensitive to PNC effects and that at present all that can be stated with any confidence is that $\mathfrak{F}\le {10}^{-4\mathrm{}}-{10}^{-5\mathrm{}}$.