Direct measurements of rate coefficients for thermal decomposition of CF3I using shock-tube ARAS technique

摘要

The kinetics of the dissociation of CF3I behind shock waves was experimentally investigated. The reaction CF3I + Ar - CF3 + 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 CF3I was obtained: k(uni) = 8.44 . 10(11 perpendicular to 0.2)exp(-182 +/- 5 kJ . mol(-1)/RT). We found that the investigated range of pressures and temperatures for the CF3I dissociation lies in the pressure transition region. Based on the Rice-Ramsperger-Kassel-Marcus theory, the threshold high and low-pressure rate constants (k(infinity) 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: k(infinity)= 1.7 . 10(15) . exp(-232 kJ . mol(-1)/RT) and k(0) = 3.3 . 10(-10)exp(-104.5 kJ . mol(-1)/RT), and the center broadening factor, which takes into account the contribution of strong and weak collisions in the transition region, is F-cent = 0.188 +/- 0.009.