Decomposition of the CF3CO radical: Pressure and temperature dependencies of the rate constant

The decomposition rate constant of the CF3CO radicals was investigated as a function of pressure and temperature, using both experimental and theoreti cal approaches. The rate constant was measured experimentally by flash phot olysis/UV absorption at one atmosphere pressure and in the 298-443 K temper ature range. Experiments were complemented by RRKM calculations combined wi th DFT quantum calculations. Ar one atmosphere pressure (N-2 + O-2), the ra te expression derived from experiments is: k = 10((11.0+/-0.7))exp(-(4214+/ -600)K/T) s(-1), in fairly good agreement with previous results obtained at different temperatures and using different experimental methods. The rate constant is in the falloff at one atmosphere pressure, near the low pressur e limit at the highest temperature and thus, the above expression should no t be used at other pressures. This explains the apparent low pre-exponentia l factor. RRKM calculations were performed and fitted to the present result s as well as to the previous ones obtained at different pressures. Those ca lculations have resulted in a comprehensive and consistent description of t he kinetic properties of this decomposition reaction. The detailed results are presented using the temperature dependent parameters of the Tree's equa tion: k(o)(T) = 1.55 x 10(-8) exp(-4420 K/T) cm(3) molecule(-1) s(-1) (buff er gas N-2 + O-2) k(infinity)(T) = 1.45 x 10(14) exp(-5878 K/T) s(-1) for F -c = 0.6.