Collision complexes in the reactions of CH+3 with C2H4 and C2H2

Abstract

We present a crossed beam study of the reactions of CH+3 with ethylene and acetylene in the relative collision energy from 0.5 to 2.0 eV. Both systems involve condensation reactions proceeding through the formation of transient collision complexes living a fraction of a rotational period which decay through ejection of one or two molecules of H2. In addition, the ethylene system also yields CH4 + C2H+3 , nominally a hydride abstraction, but also proceeding through a long-lived collision complex. Isotopic scrambling in the CD+3 +C2H4 also confirms the presence of a transient collision complex in the reaction. The similarities accompanying the flux distributions for C2H+3 and C3H+5 production in the ethylene reaction suggest a common C3H+7 intermediate. Both the acetylene and ethylene reactions yield the condensation product C3H+3 , produced through transient intermediates. The flux distribution for the ethylene reaction suggests that C3H+3 formation proceeds by sequential ejection of two H2 molecules from the initial C3H+7 intermediate. The widths of the kinetic energy distributions for C3H+3 formation imply that at least 15% of the C3H+3 products must be the more stable cyclopropenium isomer.