On the Operator Formulation of the Polyatomic Molecule Partition Function

Abstract

Abstract The Nielsen Hamiltonian of the general polyatomic molecule including anharmonicity and its resonances, Coriolis-coupling and its resonances, and rotation-vibration interaction are treated by statistical perturbation theory in its operator form. By generating function methods and operator theorems, which are treated in an appendix, cumbersome calculations with non-commuting operators are avoided. The results for H2O and SO2 agree very well with accurate numerical calculations from the literature. Qualitative conclusions on the convergence of the perturbation series are drawn from the numerical calculations for model systems.