Singlet-triplet energy splitting between D-1 and D-3 (1s(2) 2s nd), n=3, 4, 5, and 6, Rydberg states of the beryllium atom (Be-9) calculated with all-electron explicitly correlated Gaussian functions

摘要

Accurate variational nonrelativistic quantum-mechanical calculations are performed for the five lowest D-1 and four lowest D-3 states of the Be-9 isotope of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are used in the calculations and their nonlinear parameters are optimized with the aid of the analytical energy gradient determined with respect to these parameters. The effect of the finite nuclear mass is directly included in the Hamiltonian used in the calculations. The singlet-triplet energy gaps between the corresponding D-1 and D-3 states, are reported. (C) 2014 Elsevier B.V. All rights reserved.