New Empirical Equation for Atomic Masses

A new empirical equation for atomic masses has been developed. This equation has been successfully applied to atomic masses of nuclides heavier than nickel. The form used is that of an expression for the mass defect, ΔM=M-A, as a function of Z and A: ${Δ}M(A, Z)={{α}}₀+{{α}}₁A+{{α}}₂Z+{{α}}₃AZ+{{α}}₄{Z}²+{{α}}₅{A}²+{δ}.$ Because of the effects of nuclear shell structure a different set of coefficients is necessary for the different nuclear shell regions.Atomic masses calculated from this equation agree with experimental mass values to within ±{}0.5 millimass units in 75% of the 340 nuclides studied and agree to within ±{}1.5 millimass units in 95% of the nuclides. Beta-decay energies were calculated with the new equation and checked against a total of 179 experimental values. Agreement of calculated values with experiment was better than ±{}0.5 Mev in 95% of the cases and within ±{}0.25 Mev in 84%.