Ab initio study of the potential energy surfaces for the reaction C+CH→C2+H

The 18 lowest potential energy surfaces of C2H have been investigated with the complete active space multiconfigurational self-consistent-field method. We restricted our study to the doublet and quartet spin multiplicities. Twelve surfaces are issued from the ground-state reactants, while the six others are issued from the first excited state of the reactants. The approach of C toward CH shows no barrier for 6 of the 12 surfaces, obviously making the reaction possible at very low temperatures. The study of the potential energy curves along the reactant and product channels shows that the X, A, a, b, and c states of C-2 are expected to be populated by the title reaction, even at vt:very low temperatures. Moreover, six new equilibrium structures corresponding to the excited states of C2H are predicted.