Dynamics of the reaction C(3P)+SiH4: Experiments and calculations.

We conducted the reaction C(³P)+SiH₄ at a collision energy of 4.0 kcal mol^-1 in a crossed molecular-beam apparatus measuring time-of-flight mass spectra and selective photoionization. Product ions with m/z=41–43 are associated with two product channels, H₂SiCH/HSiCH₂/SiCH₃+H and H₂SiC/HSiCH/SiCH₂+H₂. Apart from daughter ions and isotopic variants of reaction products, the species observed at m/z=43 is assigned to product H₂SiCH/HSiCH₂/SiCH₃ and that at m/z=42 to product H₂SiC/HSiCH/SiCH₂. The signals observed at m/z=41 are due to dissociative ionization of silicon-carbon hydrides of these two types. We report time-of-flight spectra of products at specific laboratory angles and theoretical simulations, from which both kinetic-energy and angular distributions of products in the center-of-mass frame were derived. The release of kinetic energy is weakly dependent on the scattering angle for these two reactions. The channels for loss of H and H₂ release average translational energies of 10.5 and 16.7 kcal mol^-1, respectively. As hydrogen transfer before decomposition is facile, products H₂SiCH/HSiCH₂/SiCH₃ and H₂SiC/HSiCH/SiCH₂ exhibit mildly forward/backward preferred and isotropic angular distributions, respectively. We estimate the branching ratios of these channels for loss of H and H₂ to be roughly 6:4. The measurements of release of kinetic energy and ionization thresholds of products indicate that SiCH₃(²A^″) and SiCH₂(³A₂) are dominant among isomeric products. To explore the reaction mechanism, we computed the potential-energy surfaces for the reaction C(³P)+SiH₄. The most likely mechanism is that atom C ³P inserts into bond Si–H of SiH₄ in the entrance channel, and the reaction complex H₃SiCH subsequently isomerizes to HSiCH₃ followed by decomposition to SiCH₃(²A^″)+H and SiCH₂(³A₂)+H₂. We observed no significant evidence for the reaction C(¹D)+SiH₄. [ABSTRACT FROM AUTHOR]