Abstract
Abstract Highly accurate calculations are reported for the eleven lowest states of the 2 P Rydberg series (1 s 2 np 1 , n = 2, …, 12) of the lithium atom. The nonrelativistic wave functions of the states are expanded in terms of up to 16 000 all-electron explicitly correlated Gaussian (ECG) basis functions. The ECG exponential parameters are variationally optimized using a method that employs the analytical energy gradient determined for the parameters. The finite-nuclear-mass effects of the 6 Li and 7 Li isotopes are explicitly included in the nonrelativistic variational calculations. The results also include the leading relativistic and quantum electrodynamics energy corrections computed using the framework of perturbation theory. The calculated interstate transition energies are compared with the available experimental data. The 6 Li– 7 Li isotope shifts of the transition energies are determined.