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 Ha rtree-Fock method for field strengths ranging from zero up to 2.35 x 1 0(8) 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(-1), configuration, and in high fields, the 1s2p(-1)3d(-2) elect ronic configuration is responsible for the properties of the atom. The transition field strengths are determined. Calculations on the ground state of the Li+ ion allow us to describe the field-dependent ionizat ion energy of the Li atom. Some general arguments on the ground states of multielectron atoms in strong magnetic fields are provided.