Investigation of vibrational–rotational relaxation of formyl fluoride (HCOF) molecules

Double infrared–infrared resonance was used to measure the lifetimes of an individual vibrational–rotational level and of the whole ensemble of rotational levels belonging to the ν₄ = 1 vibrational state of HCOF molecules. For an individual vibrational-rotational state in pure HCOF we obtained pτ_R = 7.2 ±0.7 nsec·Torr. The cross section of this deactivation process was larger than that of a gaskinetic process, which was typical of the rotational relaxation of polar molecules. For mixtures with He and Kr buffer gases the deactivation constant was two orders of magnitude lower than that of pure HCOF; the experimental values were pτ = 0.7±0.1 and 1.6±0.2 μsec·Torr, respectively. The lifetimes of the ν₄ = 1 vibrational state in pure HCOF and in mixtures with He, Kr, and Ar were found to be pτ = 27 ± 3, 220 ± 20, 442 ± 40, and 371 ± 37 μsec·Torr, respectively.