Nuclidic mass formula on a spherical basis with an improved even-odd term

A nuclidic mass formula composed of a gross term, an even-odd term and a shell term is presented as a revised version of the mass formula constructed by the present authors and published in 2000. The gross term has almost the same functional form as in the previous formula, but the parameter values in it are somewhat different. The even-odd term is treated more carefully, and a considerable improvement is realized. The shell term is exactly the same as the previous one; it was obtained using spherical single-particle potentials and by treating the deformed nucleus as a superposition of spherical nuclei. The new mass formula is applicable to nuclei with Z >= 2 and N >= 2. The root-mean-square deviation from experimental masses is 666.7 keV, which is less than that of the previous mass formula, 689.8 keV.