FACTORED WAVE-FUNCTION FOR BOUND S-TYPE STATES OF 2-ELECTRON ATOMIC SYSTEMS

A simple and accurate variational wave function in which the dependenc e in the interelectronic distance is factored is proposed to describe S-type states of two-electron atomic systems. We introduce a parameter ization which generalizes the previous ones used in this same framewor k and which allows us to obtain in a simple way the wave function of b oth symmetric and antisymmetric excited states. We performed a systema tic analysis of some exact properties such as the virial theorem and t he cusp conditions and a study of both the one- and two-body densities . Finally, a comparison among the different correlation functions for these states was performed for helium. (C) 1998 John Wiley & Sons, Inc .