Prediction of 1P Rydberg energy levels of beryllium based on calculations with explicitly correlated Gaussians

Benchmark variational calculations are performed for the seven lowest 1s(2)2s np (P-1), n = 2... 8, states of the beryllium atom. The calculations explicitly include the effect of finite mass of Be-9 nucleus and account perturbatively for the mass-velocity, Darwin, and spin-spin relativistic corrections. The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian functions. Basis sets of up to 12 500 optimized Gaussians are used. The maximum discrepancy between the calculated nonrelativistic and experimental energies of 1s(2)2s np(P-1) -> 1s(2)2s(2) (S-1) transition is about 12 cm (1). The inclusion of the relativistic corrections reduces the discrepancy to bellow 0.8 cm (1). (C) 2014 AIP Publishing LLC.