Elementary deactivation processes of CHF[Ã1A″(0,0⩽v2⩽ 5,0)] after single vibronic level excitation by He, Ar and the CHF precursor CH2F2

Abstract

Time- and spectrally resolved laser-induced fluorescence of CHF(ùA″v^′₂) in single vibronic excited levels (SVL)(0 ⩽v^′₂⩽ 5) in the gas phase has been investigated at room temperature. The CHF[X¹A′(0,0,0)] source was a microwave discharge in a flow system or multiphoton dissociation (MPD) of CH₂F₂ in the fluorescence cell. Collision-free lifetimes of the states v^′₂= 4 and v^′₂= 5 were measured to be τ₀= 1.65 µs and τ₀= 1.5 µs, respectively. Deactivation rate constants of CHF[Ã(v^′₂)], (0 ⩽v^′₂⩽ 5), were determined for the quenchers CH₂F₂(X), He and Ar. Overall deactivation rate constants in [10¹³ cm³ mol^–1 s^–1] are: [graphic omitted] increasing with increasing vibrational quantum number. For Ar, the ratio of vibrational to overall deactivation was found to be in the range 0.6⩽10^–2(k_vib/k_q)⩽ 7.3, i.e. the contribution of vibration deactivation to the overall depletion of the initially excited state is small (⩽10%). Deactivation processes with a vibrational quantum change of Δv^′₂= 1 and Δ^′₂= 2, respectively, were determined to be of nearly the same importance.