REACTIONS OF THE METHYLIDINE RADICAL WITH CH4, C(2)H(2)R C2H4, C2H6, AND BUT-1-ENE STUDIED BETWEEN 23-K AND 295-K WITH A CRESU APPARATUS

The temperature dependences of the reactions of the methylidine radica l (CH) with several hydrocarbons were studied in the temperature range 23-295 K using the Rennes CRESU apparatus coupled with the pulsed las er photolysis (PLP), laser induced fluorescence (LIF) technique. All t he reactions remain very fast at low temperature. For the reactions of CH with olefins, a maximum rate is obtained at about 70 K and then th e fate coefficients slightly decrease at lower temperatures, A similar effect is observed in the data for CH+CH4 and CH+C2H6 with a maximum rate being obtained at about 40 K. The results are compared with previ ous studies where available, and the nature of the possible products i s also discussed, although this study does not enable their detection. Consequences of these new results for the chemistry of planetary atmo spheres and interstellar clouds are stressed.