Infrared double resonance spectroscopy of V-T, R relaxation of HF(v=1): Direct measurement of the high-J populations

Abstract

The V-T, R relaxation of HF(v=1) by HF is studied by infrared pulse-probe transient absorption measurements using a tunable F-center laser. It is found that a substantial fraction of the relaxation occurs through the high-lying rotational levels of v=0. The results indicate that the states J=10–14 comprise ∼20%–40% of the population in the total relaxation, with the distribution increasing rapidly with decreasing J in this range. The observed signals, corrected for cascade, correspond to the fractions: J=10, ∼10%–40%; J=11, ∼4%–10%; J=12, ∼2%–6%; J=13, ∼1%–2%; and J=14, ∼0.05%–0.35%. In addition, the V-T, R rate determined here, k=1.46±0.15×10−12 cm3 molecule−1 s−1 reconfirms previous double resonance results. Also, studies involving buffer gas addition (Ar) give no indication of ‘‘bottleneck’’ effects on the high J’s. In fact, the R–R, T rates always exceed the V-T, R rate by one to two orders of magnitude. For J=11–13, the R–R, T rates range from ∼1.2×10−10 to 6×10−11 cm3 molecule−1 s−1.