CALCULATIONS OF ENERGY-LEVELS FOR ATOMS WITH SEVERAL VALENCE-ELECTRONS

A new ab initio method for doing high-accuracy calculations for atoms with more than one valence electron is described, An effective Hamilto nian for the valence electrons is formed using many body perturbation theory for the residual cole-valence interaction, The configuration in teraction method is used then to find the energy levels of the atom. A pplication to thallium shows that this method gives an accuracy of abo ut 0.5% for the ionization potential and a few tenths of a percent for the first few energy intervals. (C) 1996 American Institute of Physic s.