QUANTUM CHEMISTRY OF HEAVY-ATOMIC MOLECULAR SYSTEMS: THE $^{2}\Sigma_{1/2}$,$^{2}\Pi_{1/2}$, AND $^{2}\Pi_{3/2}$ STATES OF THE HgH MOLECULE

Abstract

A new approach to the molecular formation of heavy atoms is discussed. In this approach the atomic core-electrons occur as a resultant exact numerical Hartree-Fock (relativistic) core-potential represented in terms of a given basis set. The core-orthogonality constraints are taken into account in terms of explicit eigenvectors of the core-Fock Hamiltonian whose eigenvalues lie below those that belong to the valence and virtual space. Also approximate ``pseudo-potential” type terms are introduced into the Fock equation to represent the orthogonality effects of those core-orbitals that are not representable by the basis set chosen. Estimates of the core-distortion and relativistic contributions are considered. Application to the $^{2}\Sigma_{1/2}$, $^{2}\Pi_{1/2}$, and $^{2}\Pi_{3/2}$ states of the HgH molecule is considered.