Chemical dynamics of cyclopropynylidyne „ c - C 3 H ; X 2 B 2 ... formation from the reaction of C „ 1 D ... with acetylene , C 2 H

The reaction between electronically excited carbon atoms, C(D), and acetylene was studied at two average collision energies of 45 kJ mol and 109 kJ mol employing the crossed molecular beam technique. The time-of-flight spectra recorded at mass to charge m/e537~C3H ! and m/e 536(C3 ) show identical patterns indicating the existence of a carbon versus atomic hydrogen exchange pathway to form C3H isomer~s!; no H2 elimination to the thermodynamically favorable tricarbon channel was observed. Forward-convolution fitting of our data shows that the reaction proceeds via direct stripping dynamics on the A8 surface via an addition of the carbon atom to the p-orbital of acetylene to form a highly rovibrationally, short lived cyclopropenylidene intermediate which decomposes by atomic hydrogen emission to c-C3H(X B2). The dynamics of this reaction have important impact on modeling of chemical processes in atmospheres of comets approaching the perihelon as photolytically generated C(D) atoms are present. © 2001 American Institute of Physics. @DOI: 10.1063/1.1330232#