Chemical laser study of the reaction F + HI by the equal-gain technique

Vacuum ultraviolet photolysis of CF
3
I provides a convenient fluorine atom source for chemical laser studies, as noted by Berry. Following Berry, we have used this source for a study of laser emission from the reaction. F + HI → HF + I,
\DeltaH = -64
kcal. Laser emission is observed from all vibrational transitions up to
\upsilon = 6 \rightarrow 5
, indicating that as much as 94 percent of the reaction energy can go into HF vibrational excitation. The
\upsilon = 4 \rightarrow 3
transition displays highest gain;
\upsilon = 4
requires about 63 percent of the available energy. The equal gain temperature technique has been used to measure the rate constant ratio,
k_{4}/k_{3}
. The result obtained,
k_{4}/k_{3} = 1.19 \pm 0.03
, is in good agreement with recent measurements based upon infrared chemiluminescence. Experiments directed at measuring the temperature dependence of such rate constant ratios were described. Equal gain measurement of the same ratio at different temperatures are possible since the highest gain transitions change with temperature. The reaction studied was F + D
2
→ DF + D,
\DeltaH = -32
kcal. CF
2
I was the fluorine source. The value of
k_{3}/k_{2}
, was found to be 1.5± 0.1 at 301 K. Preliminary data suggested a monotonic rise in the ratio as the temperature was increased, iu qualitative agreement with the molecular beam results reported by Lee et al.