Fine structure of the beryllium P 3 states calculated with all-electron explicitly correlated Gaussian functions

The recently presented general algorithm for calculating an atomic fine structure [Kȩdziorski et al., Chem. Phys. Lett. 751, 137476 (2020)CHPLBC0009-261410.1016/j.cplett.2020.137476] is employed to study the fine splitting of the lowest eight P3 states of beryllium, i.e., the 1s22snp, n=2, ,9, P3 states. All-electron explicitly correlated Gaussian functions and a finite-nuclear-mass variational method are used in the calculations. The energies of the states are augmented with the leading α2 relativistic and α3 (and approximate α4) QED corrections (α=1c is the fine-structure constant, and c is the speed of light in atomic units). The calculated results are compared with the available experimental data.