Electron affinity of 7Li calculated with the inclusion of nuclear motion and relativistic corrections

Abstract

Explicitly correlated Gaussian functions have been used to perform very accurate variational calculations for the ground states of 7Li and 7Li−. The nuclear motion has been explicitly included in the calculations i.e., they have been done without assuming the Born-Oppenheimer BO approximation . An approach based on the analytical energy gradient calculated with respect to the Gaussian exponential parameters was employed. This led to a noticeable improvement of the previously determined variational upper bound to the nonrelativistic energy of Li−. The Li energy obtained in the calculations matches those of the most accurate results obtained with Hylleraas functions. The finite-mass non-BO wave functions were used to calculate the 2 relativistic corrections =1/c . With those corrections and the 3 and 4 corrections taken from Pachucki and Komasa J. Chem. Phys. 125, 204304 2006 , the electron affinity EA of 7Li was determined. It agrees very well with the most recent experimental EA