Measurement of absolute rate data for the reactions of ground state atomic silicon Si(33PJ) with acetylenes by time-resolved atomic resonance absorption spectroscopy

Abstract

We present a kinetic study of ground state atomic silicon with acetylenic reactants. Si(3 3 P J ) was generated by the repetitive pulsed irradiation of SiCl 4 in the presence of excess helium buffer gas and the reactant R in a slow flow system, kinetically equivalent to a static system. The transient atom was then monitored by time-resolved atomic resonance absorption spectroscopy at λ = 252 nm (Si(4 3 P J ) ← Si(3 3 P J )) using signal averaging techniques. The following absolute second-order rate constants k R are reported ( T = 300 K; erros, 2σ): These rate constants constitute a new body of fundamental rate data for the atom. They are discussed within the context of nuclear recoil measurements in general for 31 Si and insertion reactions of silylenes. We also report a value of the diffusion coefficient of atomic silicon in helium of D 12 {Si(3 3 P J )−He} = 0.48 ± 0.04 (2σ) cm 2 s −1 at 1 atm ( T = 300 K).