The dynamics of the reaction D+2+C→CD++D at kinetic energies between 0.002 and 14 eV

Abstract

Absolute total reaction cross sections and product kinetic energy distributions have been measured for the reaction D+2+C→CD++D over the range of initial kinetic energies between 0.002 and 14 eV. At very low collision energies, the reaction cross section is accurately proportional to the capture cross section calculated for Π approaches of the reactants, taking into account the long-range charge-quadrupole and charge-induced dipole interactions. About 37% of close collisions on Π surfaces lead to CD++D reaction products. Reactions on Σ surfaces are inhibited at low kinetic energies by a strongly repulsive charge-quadrupole interaction at large separations. The reaction is direct at all kinetic energies, with the CD+ product scattered preferentially in the direction of the incident C atom. The reaction is extremely exoergic, and the CD+ product is formed with an internal energy very near its dissociation limit over a large range of collision energies. Although the experimental results do not give direct information on the electronic state pathways to the observed products (except that the reactants approach asymptotically on Π surfaces), the electronic state correlations suggest a low-energy adiabatic pathway to the CH+ (3Π) first excited state of the products, which is consistent with both the measured values of the reaction cross sections and the reaction energetics.