RECOMBINATION AND DECOMPOSITION OF METHYLENE RADICALS AT HIGH-TEMPERATURES

Recombination and decomposition of methylene radicals have been invest igated over a wide range of experimental conditions. It has been found that H atom forming channels play only a minor role in the reactions investigated. The rate constants for the recombination channels CH2 CH2 --> C2H2 + H-2 (1a) and C2H2 + 2H (1b) have been determined to be k(1a) = 10(15.2) (+/-) (0.2.)exp (-(50 +/- 5) kJ mol(-1)/RT) cm(3) mol (-1) s(-1) k(1b) = 10(14.3) (+/-) (0.2.)exp (-(46 +/- 5) kJ mol(-1)/RT ) cm(3) mol(-1) s(-1) in the temperature range from 1100-2700 K. The H atom channel in the decomposition of methylene in argon leading to CH +H (2b) has been found to be k(2b) = 10(15.75+/-0.15.)exp((-375 +/- 15 ) kJ mol(-1)/RT) cm(3) mol(-1) s(-1) at temperatures between 1900-2700 K. A comparison with literature data available for channel (2a) leadi ng to C+H-2 shows that the contribution of the H atom channel (2b) in the decomposition reaction of CH2 is around 10-15%. The energy of acti vation is in good agreement with the theoretically calculated value.