Prediction of 2D Rydberg energy levels of 6Li and 7Li based on very accurate quantum mechanical calculations performed with explicitly correlated Gaussian functions

Abstract

Very accurate variational nonrelativistic finite-nuclear-mass calculations employing all-electron explicitly correlated Gaussian basis functions are carried out for six Rydberg 2D states (1s2nd, n= 6, . . . , 11) of the 7Li and 6Li isotopes. The exponential parameters of the Gaussian functions are optimized using the variational method with the aid of the analytical energy gradient determined with respect to these parameters. The experimental results for the lower states (n = 3, . . . , 6) and the calculated results for the higher states (n = 7, . . . , 11) fitted with quantum-defect-like formulas are used to predict the energies of 2D 1s2nd states for 7Li and 6Li with n up to 30