On the interaction hyperpolarisability of He 2, He 3 and Ne 2. An AB initio study

Abstract

The interaction hyperpolarisability of He 2 Ne 2 and He 3 as well as the three-body contribution to the latter are discussed. The calculations have been performed using a computational procedure which relies on an ab initio wave function, McWeeny's coupled Hartree-Fock perturbation theory and an efficient algorithm for the determination of the hyperpolarisability, starting from a non-orthogonal basis set. The values have been corrected for the basis set superposition error by employing the function counterpoise method.