ELECTRON-SPIN ELECTRON-SPIN, ELECTRON-SPIN ROTATION INTERACTIONS, AND QUARTIC CENTRIFUGAL-DISTORTION TERMS FOR AN OPEN-SHELL DIATOMIC MOLECULE VAN-DER-WAALS BONDED TO A CLOSED-SHELL PARTNER

Effective Hamiltonians Hsr, Hss, Hλd, Hcd, and their matrix elements are derived for calculating electron-spin rotation, electron-spin electron-spin splittings, and centrifugal distortion correction terms to electron-spin electron-spin interaction and rotational energy levels, respectively. This formalism is valid for a near rigid, nonlinear planar open-shell complex consisting of an open-shell diatomic unit in an electronic state described by 2S+1Λ, where Λ = Σ, Π, Δ, Φ, etc,; S ≥ 1 2, and a closed-shell partner (a rare gas atom or a closed shell diatomic molecule). Electron-spin electron-spin interaction and its centrifugal distortion correction terms (described by Hss and Hλd, respectively) are needed only for complexes containing an open-shell diatomic unit with S > 1 2, whereas electron-spin rotation and centrifugal distortion correction terms to rotational energy levels (described by Hsr and Hcd respectively) are required for complexes containing an open-shell diatomic unit with S ≥ 1 2. For calculating effects of Hsr, Hss, Hλd, and Hcd on rotational energy levels in the mentioned types of complexes, the total Hamiltonian is written as H = Hrot + Hso + Hq + Hsr + Hss + Hλd + Hcd. Rotational energy levels are then obtained by numerically diagonalizing this Hamiltonian matrix for each given J. Matrix elements of Hrot, Hso, Hq, and calculations of relative intensities in spin and orbitally allowed transitions in the open-shell diatomic fragment and in rotationally or vibrationally allowed transitions in the closed-shell partner (when the closed-shell partner is a dipolar diatom) are the same as described in our previous work (W. M. Fawzy and J. T. Hougen, J. Mol. Spectrosc.137, 154-165 (1989)). A brief discussion of the matrix elements of Hsr, Hss, HΛd, Hcd, and their inclusion in our previous computer program for calculating rotational energy levels and relative intensities of allowed transitions is given. © 1993 Academic Press Inc.