Photolytic production of S(1S) from OCS by two-quantum and vibrationally dependent mechanisms

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Abstract
Studies of photolytic production of S(1S) atoms by two-photon dissociation of OCS at 193 nm are reported. The excited sulfur atoms are detected by observation of the collisionally-induced XeS(2 1Σ+ →1 1Σ+) emission near the S(1S→1D) atomic line at 773 nm. The measured OCS two-quantum absorption cross section is in accord with theoretical estimates based on previous established spectroscopic data. In addition, it is found that excitation of the OCS (ν2) bending vibration by CO2 laser irradiation causes the S(1S) yield to be considerably enhanced. The experimental data obtained indicate the presence of vibrational mode specificity in the mechanism of photolytic enhancement. Vibrationally dependent quenching arising from OCS† +S(1S) collisions is also observed. The mechanisms of vibrational enhancement are discussed in relation to their general applicability for photolytic production of electronically excited species.