The sextic centrifugal distortion terms for an open-shell complex consisting of a diatomic molecule in a (2S+1)Sigma electronic state and a closed-shell partner

摘要

An effective Hamiltonian for calculating rotational energy levels of an open-shell diatomic molecule, in a (2S+1)Sigma electronic state, weakly bonded to a closed-shell partner was presented (W. M. Fawzy, J. Mel. Spectrosc. 191., 68-80 (1998)). The Hamiltonian was given as H = H-ev + H-rot + H-sr + H-ss + H-cd + H-sred + H-ssed, where all the quartic centrifugal distortion correction terms were included in the Hamiltonian term H-cd but the sextic centrifugal distortion terms were ignored. This Hamiltonian is useful in cases where the complex has a well-defined equilibrium geometry and if the barrier to large-amplitude motion is large compared to the rotational constant of both the closed-shell molecule and its paramagnetic partner; if the barrier to large-amplitude motion is small compared to the rotational constant of one or both of the fragments, then a different treatment is required. In this paper, we introduce the new Hamiltonian terms H-cd(sex(A)) and H-cd(sex(S)) which represent the sextic centrifugal distortion correction terms for an asymmetric rotor. We also introduce all the nonvanishing matrix elements of each of the H-ed(sex(A)) and H-cd(sex(S)) operators. These operators and their matrix elements are required for calculating the rotational energy levels of relatively high J values in the described type of weakly bonded open-shell complexes. The terms H-cd(sex(A)) and H-ed(sex(S)) and their matrix elements are also valid for any stable asymmetric rotor in a nondegenerate electronic stab. A brief discussion of the new Hamiltonian terms and their matrix elements is given. (C) 2000 Academic Press. [References: 13]