Collision dynamics of intermode energy flow in laser pumped polyatomic molecules: CH3F

Abstract

Subsequent to placing excess vibrational population in the ν3C–F stretching mode of CH3F by a Q-switched CO2 laser, the time dependence of fluorescence signals from the overtone level 2ν3 and from all other vibrational fundamental levels has been monitored and analyzed. The nearly resonant, ladder climbing process CH3F(ν3)+CH3F(ν3) ⇄CH3F(2ν3)+CH3F(O)+18 cm−1 reaches steady state in about 3.3 gas kinetic collisions. The excess vibrational energy contained in the ν3 mode is transferred to the remaining CH3F modes on a longer timescale. Direct coupling exists between ν3 and ν6 and between ν6 and ν2,ν5: CH3F(ν3)+CH3F⇄CH3F(ν6)+CH3F−133 cm−1 CH3F(ν6)+CH3F⇄CH3F(ν2,ν5)+CH3F−284 cm−1. These two processes have been found to reach steady state in 30 and 120 gas kinetic collisions, respectively, in pure CH3F. No evidence for the direct coupling between ν3 and ν2,ν5 has been found. Equilibration of the C–H stretch levels ν1, ν4 with the rest of the CH3F vibrational levels via the fairly efficient ladder climbing process 2CH3F(ν2,ν5) ⇄CH3F(2ν2,2ν5)+CH3F(O)+87 cm−1 which populates the overtones 2ν2,2ν5, followed by crossover between the Fermi mixed levels 2ν5 and ν1 CH3F(2ν5)+CH3F⇄CH3F(ν1)+CH3F is consistent with the data obtained in the present experiments.

Ion chemistry of the stratosphere

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Spectroscopy and energetics of the acetylene molecule: dynamical complexity alongside structural simplicity

“…They demonstrate that there is no general rule to predict whether J-resolved V-V transfer kinetics will be enhanced or suppressed by perturbative mixing of vibrational or rovibrational basis states, given the subtlety of interferences between diagonal matrix elements of those basis states [58,59,315,360]. This contradicts the widely held intuition that intramolecular perturbations tend to enhance V-V transfer [312][313][314]369], or the more specific statement [370] that 'a greatly enhanced energy transfer is invariably found' in the presence of perturbative mixing of vibrational basis states.…”

Vibrational Relaxation of the 2v5 Overtone of CDCl3 Highly Excited by a Tea CO2 Laser

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