A REVISED SEMIEMPIRICAL ATOMIC MASS FORMULA

Abstract

A new mass formula has been constructed which contains volume and surface energies, each with a symmetry energy contribution, Coulomb and Coulomb exchange energies, and shell correction and pairing energies. A nuclear model with a trapezoidal radial-density distribution was used. The central density was assumed constant, and the dimensions were adjusted to fit the Stanford electron-scattering results. The symmetry energy coefficients were determined by a least-squares fit to the valley of beta stability. The volume and surface energy coefficients were determined by a least-squares fit to 89 odd–odd masses uniformly spaced in mass number. The shell correction and pairing energies were assumed to be independent functions of the proton and neutron numbers; they were empirically determined from the differences between masses computed from the formula without corrections and those tabulated by Wapstra and Huizenga. The median energy difference between the corrected formula and the Wapstra–Huizenga masses is about 300 kev. Some remarks are made concerning the implication of these results for nuclear deformations and fission thresholds.