A crossed beam scattering study of reactions in the system acetylene cation-acetylene: formation of C_2HD~(+ centre dot) in C_2D_2~(+ centre dot) + C_2H_2 and formation of C_4H_3~+ and C_4H_2~(+ centre dot) in C_2H_2~(+ centre dot) + C_2H_2 collision

摘要

Dynamics of chemical reactions in the system acetylene cation-acetylene was investigated in crossed beam scattering experiments. Relative cross sections of formation of various products at T = 2.5 eV were C_4X_3~+: C_4X_2~~(+ centre dot): C_2X_2~(+ centre dot) = 1.0:0.55:0.17 (X = H, D). C_2X_2~(+ centre dot) (C_2HD~(+ centre dot) from C_2D_2~(+ centre dot) + C_2H_2 collisions) traces the decomposition of an intermediate complex C_4X_4~(+ centre dot) backward to reform the reactants; the mean lifetime of the intermediate is longer than about 5 ps and its geometry in the critical configuration close to linear. The products C_4H_3~+ and C_4H_2~(+ centre dot) are formed in exoergic reactions by the decomposition of a long-lived intermediate C_4H_4~(+ centre dot) of prolate geometry in its critical configuration. About 15% of the energy available at T = 1.5 eV in the latter two processes may be expected to be deposited as rotational energy of the product ion.