Relative populations of vibrationally excited CO produced in pulse-discharged CS2+O2+ He mixtures

Lasing was initiated by a fractional microsecond pulse discharge (≈ 15 kV) in flowing CS2+ O2+ He mixtures, maintained at about 3 torr. The cavity was grating controlled, such that resonance was maintained for selected rotational lines of specified vibrational transitions. The measured τd(intervals between termination of the discharge and initiation of lasing) followed a characteristic sequence; the minimum delay ( s) occurred for the 12 → 11 transition, with longer times for higher and lower upper vibrational states. At a CS2partial pressure of 0.05 torr, τdwere 50μs or less for transitions 14 → 13 to 5 → 4. These intervals are too short for signifigant vibrational redistribution to occur via processes. Hence the recorded delay sequence was explained on the basis of the initially generated distribution of vibrationally excited CO. Our data indicated: . The reliability of these ratios depends on the particular transition; we estimate a factor of 2 for due to the initial uncertainty of the ratio. The relative populations were also estimated from relative chemiluminescence intensities recorded under conditions identical to laser operation but in the absence of mirrors. While this distribution is in agreement with that reported from other laboratories for , there is a significant difference for the range, in that substantial fractions are generated in the low υ states.