Reactions of C(~1D) with H_2, HD and D_2: kinetic isotope effect and the CD/CH branching ratio

摘要

Electronically excited carbon atom C(~1D) was produced by the 308 nm two-photon dissociation of C_3O_2. CH and CD radicals produced by the reactions of C(~1D) + H_2, HD and D_2 were probed by laser-induced fluorescence. The nascent rotational state distributions of CH(v = 0) and CD(v = 0) were measured under single collision conditions. The distributions measured in the present study were close to those obtained in the previous studies using the 157 nm photodissociation. The rate constants at the room temperature were measured to be (2.0 ± 0.6) * 10~(-10), (1.7 ± 0.4) * 10~(-10) and (1.4 ± 0.3) * 10~(-10) cm~3 molecule~(-1) s~(-1) for the reactions with H_2, HD and D_2, respectively. The CD/CH branching ratio in the C(~1D) + HD reaction was determined to be 1.6 ± 0.1. The preference of the CD production suggests that this reaction proceeds mainly via the HCD intermediate complex.