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(A1A″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[A(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(kvib/kq)⩽ 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.