Laser emission from CO formed in the flash-initiated reactions of O(3 P) atoms with CS and CSe

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Abstract
A study has been made of the laser emission from vibrationally excited CO (CO) formed in the reactions: O(3P)+ CS → CO + S + 356 kJ mol–1(1) and O(3P)+ CSe → CO + Se +∼494 kJ mol–1, (5), with O atoms being produced directly by flash photolysis of SO2. Comparison of the emission from CS2+ SO2 with that from CS2+ O2 established (a) that excitation and quenching of SO2 can lead to appreciable heating and as a result lower gains, and (b) that relaxation of CS†, before it reacts, by SO2 and free S atoms modifies the laser output significantly. The rise in temperature can be moderated by addition of inert gas or SF6, but the latter must be used with care as it also relaxes the higher levels of CO† efficiently. Oscillation has been observed on all vibrational transitions from (20, 19) to (9, 8) with mixtures containing CSe2 and SO2; the delay times before individual transitions appeared are consistent with the CO vibrational distribution predicted from infra-red chemiluminescence experiments. The absence of lower transitions is probably due to relaxation in the processes CO(v)+ Se(3P2)→ CO(v– 1)+ Se(3P1)(7) which are close to resonance when v∼7. Once care was taken to minimise the effects of gas heating, the overall outputs from the three lasers, i.e., CS2+ O2, CS2+ SO2 and CSe2+ SO2, were roughly comparable.

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