Mass Surfaces

We examine in the light of recent experimental data smooth mass surfaces which may be placed in the form $M-A={\Delta }_m\mathrm{}\left(A\right)+J\left(A\right)\mathrm{}{[D-D_m\mathrm{}(A\left)\right]}^2,$ where ${\Delta }_m\mathrm{}\left(A\right)\mathrm{}$, $D_m\mathrm{}\left(A\right)\mathrm{}$, and $J\left(A\right)\mathrm{}$ are key functions which characterize the mass surface and $D=N-Z$ is the neutron excess. We here attempt to find an optimum set of key functions and to evaluate various semiempirical key functions now in use.