Abstract:
We have performed very accurate quantum-mechanical calculations for the two lowest S states of the lithium
atom in order to determine the transition energy. In the nonrelativistic part of the calculations performed using
the variational method, we explicitly included the nuclear motion. The nonrelativistic wave function was
expanded in terms of explicitly correlated Gaussian functions. Next, this wave function was used to calculate
the leading 2 relativistic correction is the fine-structure constant and the 3 QED correction. We also
estimated the 4 QED correction by calculating its dominating component. The results obtained with Gaussians
are compared with the most accurate results obtained recently with the Hylleraas-type basis functions