GROUND STATE OF THE LITHIUM ATOM IN STRONG MAGNETIC FIELDS

The ground and some excited states of the Li atom in external uniform magnetic fields are calculated by means of our two-dimensional mesh Hartree-Fock method for field strengths ranging from zero up to $2.35\ifmmode\times\else\texttimes\fi{}{10}^{8}\phantom{\rule{0ex}{0ex}}\mathrm{T}$. With increasing field strength, the ground state undergoes two transitions involving three different electronic configurations: for weak fields, the ground-state configuration arises from the field-free ${1s}^{2}2s$ configuration; for intermediate fields, it arises from the ${1s}^{2}{2p}_{\ensuremath{-}1}$ configuration, and in high fields, the ${1s2p}_{\ensuremath{-}1}{3d}_{\ensuremath{-}2}$ electronic configuration is responsible for the properties of the atom. The transition field strengths are determined. Calculations on the ground state of the ${\mathrm{Li}}^{+}$ ion allow us to describe the field-dependent ionization energy of the Li atom. Some general arguments on the ground states of multielectron atoms in strong magnetic fields are provided.