Nascent vibrational distributions and relaxation rates of diatomic products of the reactions of O(1D) with CH4, C2H6, CH3F, CH2F2 and CHF3 studied by time resolved Fourier transform infrared emission

Time resolved Fourier transform infrared (TRFTIR) emission has been used to study the reactions of CH4, C2H6, CH3F, CH2F2 and CHF3 with O(1D). One hundred and ninety-three nanomters photolysis of N2O was used to prepare O(1D), and emission analysed from OH(ν = 1–4) for the two hydrocarbons and HF(ν = 1–6) from CH3F, CH2F2 and CHF3. For the O(1D) + CH4 reaction, the nascent OH vibrational distribution showed a population inversion between ν = 1 and 2, and was in excellent agreement with previous laser induced fluorescence and TRFTIR data, as well as with quasi-classical trajectory calculations. Time resolved populations were analysed to yield rate constants for vibrational relaxation of OH(ν) with CH4, and found to be consistent with stepwise deexcitation rather than chemical removal being dominant. Reaction with C2H6 produced a monotonically decreasing population in ν = 1–4 and more rapid relaxation rates than those with methane. For the fluorinated methanes, nascent vibrational populations in HF(ν = 1–6) were measured and shown to be very similar, all monotonically decreasing with ν, and fitting the same vibrational surprisal plot, showing a larger than statistical partitioning of the available energy in vibration. Relaxation rate constants of HF(ν) with the parent fluorinated methane showed values, which increased with increasing H atom content.