Evidence for Nonadditivity of Nucleon Moments in Heavy Nuclei

Abstract

This paper is an attempt to evaluate additional evidence for the nonadditivity of nucleon moments and to correlate it with the evidence provided by the existence of the anomaly in the ${\mathrm{H}}^{3}$, ${\mathrm{He}}^{3}$ moments. Attention is first given to the deviations of the static moments of heavy nuclei from the Schmidt lines. This is shown to be an unreliable and ambiguous source of information because the moments are so sensitive to deviations from pure shell model wave functions. Furthermore, the observed differences from the Schmidt lines are opposite in sign and much larger in magnitude than would be expected on the basis of ${\mathrm{H}}^{3}$ and ${\mathrm{He}}^{3}$, so they could only be ascribed to a nonadditivity effect if that were a many-body effect. Much more reliable information is shown to be provided by the lifetimes of certain "forbidden" magnetic dipole transitions in heavy nuclei. These are the radiative processes which seem to involve one-particle transitions with $\ensuremath{\Delta}l=2$; hence they are forbidden on the basis of the ordinary additive moment. Here the influence of reasonable deviations from shell model functions is quite small, so the existence of the transitions is good evidence for a nonadditive contribution to the moment operator. Furthermore, the magnitude of the effect is quite compatible with what would be expected on the basis of the ${\mathrm{H}}^{3}$, ${\mathrm{He}}^{3}$ moment anomaly.