Theoretical study of the transition probabilities among the three lowest electronic states of the SeS molecule

Abstract

Spin-perturbed CI wavefunctions are reported for the X ³Σ⁻ electronic states of the SeS molecule. The Breit-Pauli approach is employed using the one- and two-electron spin-orbit operator as the perturbing hamiltonian and a zeroeth-order basis of CI eigenfunctions generated by the standard multireference single- and double-excitation (MRD-CI) formalism. Transition moments are reported between each of the above states for electric and magnetic dipole and electric quadrupole radiative processes, and these results are compared with recent experimental high resolution data obtained by Fink, Kruse, Ramsay and Wang. Generally good agreement is found between computed and observed ratios of such quantities, but the absolute values of the computed transition moments are uniformly found to be only somewhat less than half as large as the corresponding observed results. A simple formula is presented which relates the magnetic moments of the b ¹Σ⁺-X ³Σ1− transitions to twice the square root of the ratio of two observable energy differences and this result promises to be useful in future experimental studies attempting to estimate line strengths for this type of band system. On this basis arguments are also presented supporting the view that the computed absolute intensities may be more accurate than would appear from the original experimental assessment of the SeS spectroscopic data.