High-intensity laser photolysis of OCS at 157 nm: S(1S) production, photoionization, and loss

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Abstract
We have observed the production of significant concentrations of electrons in high‐intensity pulsed‐laser photolysis of OCS to S(1S) at 157 nm. These results imply a photoionization cross section for S(1S) of 2.6×10−19 cm2. We have measured the quenching of S(1S) for a variety of conditions, including incident laser fluences of 100 mJ/cm2 and initial S(1S) densities of 3×1016 cm−3. Quenching by electrons can be minimized by adding diluents such as SF6 or CF4. We interpret our observed S(1S) decay rates in terms of quenching by S(3P) with a rate constant of 3×10−11 cm3 sec−1 and by CS [and/or O(3P)] with a rate constant near 2×10−10 cm3 sec−1. The measured S(1S) lifetime decreases with increasing initial S(1S) density, reaching a value of about 1 μsec at a S(1S) density of 3×1016 cm−3. The quantum yield for S(1S) production is found to be high (near 0.8) and independent of incident laser flux or added diluent pressure. These storage times and production efficiencies are consistent with the possible use of the S(1S) →S(1D) transition as an efficient high‐energy‐storage laser.