Electron-electron correlation in a four-electron atomic system

Abstract
Electron-electron correlations in four-electron atomic systems are studied under a two-shell model. The eigenfunctions with 1=0, s=0 and parity even are extracted through a variational procedure with a basis set of functions constructed from Coulomb-modified single-electron functions. Three types of states are selected for discussion; the interest is in the qualitative aspect and the emphasis is placed on the quadruple-excited states. Geometric features of related states and some possible modes of internal motion have been found.