DETERMINATION OF THE MOLECULAR-CONSTANTS FOR INTERACTING BRIGHT AND DARK STATES - ANALYSIS OF THE HIGH-RESOLUTION INFRARED-SPECTRUM OF THE NU(8) BAND OF SULFINE, H2CSO

Gas-phase infrared spectra of the transient molecule sulfine, H2CSO, have been recorded in pyrolysis experiments using methanesulfinyl chloride or dimethyl sulfoxide as starting materials. Two strong vibrational fundamentals, upsilon(4) (a’, 1175 cm(-1)) and upsilon(8) (a ’’ 762 cm(-1)), have been observed at low resolution in the 1400-700 cm(-1) region. The upsilon(8) band has been recorded at high resolution and a detailed analysis of the rotational structure has been carried out. Numerous excited state perturbations result from Δ K-a\ = 2 A-type and Δ K-a\ = 1 B-type Coriolis interactions with the 7(2) vibrational state at 784.2 cm(-1). Although 2 upsilon(7) band transitions could not be directly observed, a complete analysis of the perturbed rotational, structure has been possible, using a Hamiltonian which includes both types of Coriolis interactions. Accurate molecular constants have been obtained for both states with only two interaction constants, one for each mechanism. A few weak perturbations at very high K-a values could not be fitted with this scheme and are assigned to high order Coriolis interactions with the 6(1) level at 866 cm(-1). (C) 1995 Academic Press, Inc.