Beryllium Atom from Weak to Strong Magnetic Fields

Abstract

The energy levels involving the 10+, 1/3(−1)+, and 3(−1)− states of the beryllium atom in magnetic fields of 0–10 a.u. (1 a.u. corresponding to 4.7011 × 105 T) are investigated. To deal with the four-electron atomic system in magnetic fields, two related methods based on the anisotropic Gaussian basis set are applied. In the field region of 0 ≤ β < 0.5 a.u., owing to the relatively weak correlation between an inner core electron and an outer valence electron, we apply the freezing full-core method. In the field region of 0.5 ≤ β ≤ 10 a.u., we carry out the full-core-plus-correlation calculation, which has a better consideration about the additional correlations. Compared to the full configuration-interaction method, significant improvement on precision of energies of spin-singlet states is achieved. For spin-triplet states, energies of similar precision are attained using a smaller basis set. The corresponding one-electron ionization energies are presented and analyzed.