Explicitly correlated Gaussian calculations of the ²D Rydberg states of the boron atom

Accurate non-relativistic variational calculations are performed for the seven lowest members of the ²D Rydberg series (1s ²2s2p ², and 1s ²2s ²nd, n 3,⋯, 8) of the boron atom. The wave functions of the states are expanded in terms of all-electron explicitly correlated Gaussian basis functions and the effect of the finite nuclear mass is directly included in the calculations allowing for determining the isotopic shifts of the energy levels. The Gaussian basis is optimized independently for each state with the aid of the analytic energy gradient with respect to the Gaussian parameters. The calculations represent the highest accuracy level currently achievable for the considered states. The computed energies are compared with the available experimental data.