Atomic fine-structure calculations performed with a finite-nuclear-mass approach and with all-electron explicitly correlated Gaussian functions

Abstract

A general algorithm for calculating an atomic fine structure is developed and implemented. All-electron explicitly correlated Gaussian functions and a finite-nuclear-mass (FNM) variational method are used in the approach. The leading α2 relativistic and α3 (and approximate α4) QED corrections are accounted for (α is the fine-structure constant). The approach is tested in calculations of 3P states of the helium and beryllium atoms. The results are compared with experimental data and the systematic deviations -0.002 cm−1 and -0.7 cm−1 are found for 3PJ=0,1,2 excitation energies of 4He and 9Be, respectively.