MASSES OF NUCLEI IN ISOBARIC SEQUENCES

Abstract

The semiempirical mass formula is known to give a rough fit to the general trend of atomic masses. A detailed correlation to within 0.5 Mev. or less is attempted between observed atomic mass-differences and the predictions of a semiempirical liquid drop formula generalized to include terms which depend on angular momentum in the way suggested by the nuclear shell model. For fixed A, it is found that, allowing for these "spin terms", the Z-dependence is parabolic. The variations of the different parameters with A and with shell changes are studied. It is found that, when close agreement with experimental values of mass is required, certain "constants" of the liquid drop formula are in fact quite dependent on A. This is interpreted to mean that the A- or Z-dependence of the formula is incomplete. Nevertheless, an empirical method of extrapolating unknown masses is suggested.