Fast-Flow Study of the CH + CH Reaction Products

The multichannel CH + CH reaction was studied, at room temperature, in a low-pressure fast-flow reactor. CH was obtained from the reaction of CHBr 3 with potassium atoms. An intense chemiluminescence from C 2 H(A 2 Π) and a much weaker one from C 2 (d 3 Π g ) were observed. The C 2 H(A 2 Π) emission spectrum appeared as a continuum extending from 380 nm to the limit of our detection range at 800 nm. C 2 (d 3 Π g ) was specifically produced in the v = 2 level, and the relative ratio C 2 (d 3 Π g )/C 2 H(A 2 Π) was proportional to the total pressure, this behavior being attributed to a production of C 2 by induced collision crossing states from excited vinylidene to the surface leading to C 2 (d 3 Π g ) + H 2 . Relative product branching ratios were determined over the channels yielding the following atoms: H + C 2 H, >90%; C + CH 2, <10%.