Vibrational relaxation of highly excited diatomics. V. The V–V channel in HF(v)+HF(0) collisions

The V–V fraction in HF self-relaxation is determined in fast-flow infrared chemiluminescence experiments through the consistent accounting of all HF(v) populations in partially relaxed mixtures. The v-level specific, fractional V–V probabilities fv are measured for v=2 and 3 using the F+H2 and F+CH4 generating reactions, and estimates are obtained for v=4 to 7 using F+HBr and H+F2 data. A consistent set of fv’s is 0.55±0.10, 0.30±0.10, 0.15±0.10, and zero for v=2, 3, 4, and 5 to 7, respectively. These values are compared with one recent laser measurement for v=2 and with the theoretical predictions of semiclassical trajectory calculations.