Electron Magnetic Perturbation in Diatomic Molecules of Hund's Case b

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Abstract
The perturbation due to spin-orbit and spin-spin interactions has been studied for a Hund's Case b diatomic molecule with two outer electrons. The interactions are expressed as scalar products of two irreducible tensors and Racah's method is used to compute the off-diagonal matrix elements between states differing by ΔΛ=0, ±1, ±2; ΔS=0, ±1; ΔN=0, ±1, ±2. The matrix elements are used to study the ``forbidden predissociation'' of the metastable c 3Πu state of H2 via the repulsive b 3Σu+ state, which was the mechanism assumed by Lichten to account for the differences in the lifetimes of fs levels of c 3Πu state of H2. The relative lifetimes of fs levels thus calculated are in reasonable agreement with Lichten's measurements. The N dependence of the matrix element of spin-orbit interaction is shown to be similar to that of spin-spin interaction. The second-order perturbations via intermediate states are found to have N dependence similar to that of the first order when N is large. The interference among different transition processes between two states is discussed. The symmetric top wavefunction is used as the rotational wavefunction and its symmetry property under inversion which is necessary for this study is reviewed.