Quasirelativistic valence ab initio calculation of the potential energy curves for the Hg–rare gas atom complexes

Abstract

Results of large-scale valence ab initio calculations of potential energy curves for ground and several excited states of the Hg–rare gas (RG) van der Waals molecules are reported. In the calculations, the Hg 20+ and RG 8+ cores are simulated by energy-consistent pseudopotentials which also account for scalar-relativistic effects and spin–orbit (SO) interaction. Potential energies in the ΛS coupling scheme have been evaluated by means of ab initio complete-active-space multiconfiguration self-consistent field (CASSCF)/complete-active-space multireference second-order perturbation theory (CASPT2) calculations, while the SO matrix has been computed in a reduced CI space restricted to the CASSCF level. Finally, the Ω potential curves are obtained by diagonalization of the modified SO matrix (its diagonal elements before diagonalization substituted by the corresponding CASPT2 eigenenergies). The calculated potential curves, especially the derived spectroscopic parameters for the ground and several excited states of the Hg–RG species are presented and discussed in the context of available experimental data. The theoretical results exhibit very good agreement with experiment.