  Present atomic theory provides accurate and reliable results for atoms with a
small number of valence electrons. However, most current methods of
calculations fail when the number of valence electrons exceeds four or five.
This means that we can not make reliable predictions for more than a half of
the periodic table. Here we suggest a modification of the CI+MBPT
(configuration interaction plus many-body perturbation theory) method, which
may be applicable to atoms and ions with filling d and f shells.

Atomic Physics;Chemical Physics