EXCHANGE INTERACTION ENERGY BETWEEN 2 ONE-ACTIVE ELECTRON ATOMS AT LARGE DISTANCES

Developed formulas for the exchange interaction energy between two neu tral one-active electron atoms interacting at large distances R are pr esented in terms of known basic integrals obtained from an asymptotic method for the alkali dimers M(2) dissociating to M(ns) + M(ns), M(ns) + M(n'l), l = 0,...,3 and M(np) + M(np). Detailed illustrative numeri cal results are displayed for the molecular states of Na-2 dissociatin g to the limit Na(3s) + Na(3p). Comparisons with very accurate ab init io results as well as with some available experimental data show that accurate potential energy curves for these excited states may be obtai ned in a very large range of internuclear distances by connecting ab i nitio curves for small and intermediate values of R with long-range cu rves obtained as the sum of usual multipolar Coulombic energy and asym ptotic exchange energy.