Direct measurements of rate coefficients for thermal decomposition of CF ₃ I using shock—tube ARAS technique

The kinetics of the dissociation of CF 3 I behind shock waves was experimentally investigated. The reaction CF 3 I + Ar → CF 3 + I + Ar was studied at temperatures between 900 and 1250 K and pressures of 2–3 bar. For this purpose, the time profiles of the concentration of atomic iodine were measured using a highly sensitive atomic resonance absorption spectroscopy method at a wavelength of 183.04 nm. From these data, the experimental value of the dissociation rate constant of CF 3 I was obtained: . We found that the investigated range of pressures and temperatures for the CF 3 I dissociation lies in the pressure transition region. Based on the Rice-Ramsperger–Kassel–Marcus theory, the threshold high and low-pressure rate constants ( and k 0 ) and falloff curves are calculated for the temperatures of 950–1200 K. As a result of this calculation, the threshold rate constants could be evaluated in the forms: and , and the center broadening factor, which takes into account the contribution of strong and weak collisions in the transition region, is .