Physical properties of normal two-electron systems considering correlation

A number of correlated wave functions having two types of correlation for the ground state of helium iso-electronic systems, have been proposed in the following forms (a.u.): Graphics We have used Monte- Carlo method to optimize the sets of the exponential correlation parameter mu(i) along with the other nonlinear variation parameters A, B to determine quite accurate eigen energies and other physical properties within the framework of the Rayleigh-Ritz variational principle. The corresponding eigen energies is an element of(a.u.) and other observable quantities, such as, magnetic susceptibility X(cm(3)) are in good agreement with the accurate results available in the literature. The wave functions may be of use in atomic collision problems where correlations between the electrons play an important role.