ROTATIONAL ENERGY-LEVELS AND LINE-INTENSITIES FOR (2S-(2S+1)SIGMA TRANSITIONS IN AN OPEN-SHELL DIATOMIC MOLECULE WEAKLY BONDED TO A CLOSED-SHELL PARTNER(1)SIGMA)

This paper concerns rotational energy levels and line intensities for electronic, vibrational, and microwave transitions in an open-shell co mplex consisting of an open-shell diatomic molecule and a closed-shell partner. The electronic state of the open-shell diatomic fragment is a (2S+1)Sigma state, where S greater than or equal to 1/2, the close-s hell partner could be a rare gas atom or a diatomic molecule or a plan ar polyatomic molecule. We are considering a near-rigid rotor model fo r a nonlinear complex, taking into account thoroughly all effects of t he electron spin and the quartic centrifugal distortion correction ter ms. The total Hamiltonian is expressed as H=H-rot+H-sr+H-ss+H-cd+H-src d+H-sscd. We have derived all the nonvanishing matrix elements of the Hamiltonian operators in the molecular basis set. The rotational energ y levels are calculated by numerical diagonalization of the total Hami ltonian matrix for each J value. The nonvanishing matrix elements of t he electric dipole moment operator are derived in the molecular basis set for electronic, vibrational, and microwave transitions within the complex. Expectation values of the quantum numbers and of the parities of the rotational states are derived in the molecular basis set. Rela tive intensities of the allowed rotational transitions, expectation va lues of the quantum numbers and the parities are calculated numericall y in the space of the eigenvectors obtained from diagonalization of th e Hamiltonian matrix. The formalism and the computer program of this p aper are considered as extensions to our previous work [W. M. Fawzy an d J. T. Hougen, J, Mol. Spectrosc. 137, 154-165 (1989); W. M. Fawzy, J . Mol. Spectrosc. 160, 84-96 (1993)] and are expected to be particular ly useful for analyzing and fitting high-resolution spectra of weakly bonded oxygen complexes. A brief discussion of the Hamiltonian operato rs, the matrix elements, and the computer program is given. (C) 1998 A cademic Press.