Recombination and Decomposition of Methylene Radicals at high Temperatures

Recombination and decomposition of methylene radicals have been investigated 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 CH 2 +CH 2 °C 2 H 2 +H 2 (1a) and C 2 H 2 +2H (1b) have been determined to be k 1a = 10 15.2·.0.2 Σ 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 −l in the temperature range from 1100–2700 K. The H atom channel in the decomposition of methylene in argon leading to CH+H (2 b) has been found to be k 2b = 10 15.75±0.15 ·exp((‐375±15) kJ mol −1 / RT ) cm 3 mol −1 s −l at temperatures between 1900–2700K. A comparison with literature data available for channel (2a) leading to C+H 2 shows that the contribution of the H atom channel (2b) in the decomposition reaction of CH 2 is around 10–15%. The energy of activation is in good agreement with the theoretically calculated value.