Kinetic study of the reactions of ground-state silicon atoms, Si(3 3 P J ), with buta-1,3-diene and but-2-yne

Abstract

We present a kinetic study of the reaction between atomic silicon in its electronic ground state, Si(3 ³P_J), and the molecules buta-1,3-diene and but-2-yne. Si(3 ³P_j) was generated by the repetitive, pulsed irradiation of SiCl₄ in the presence of an excess of helium in a flow system kinetically equivalent to a static system, and monitored by time-resolved atomic resonance absorption spectroscopy at λ= 252 nm [Si(4 ³P_J)â†� Si(3 ³P_J)] using signal averaging. The following absolute second-order rate constants (300 K, errors 2σ) are reported: k_R(buta-1,3-diene)= 1.1 ± 0.2 × 10^–9 cm³ molecule^–1 s^–1, k_R(but-2-yne)= 6.3 ± 0.9 × 10^–10 cm³ molecule^–1 s^–1. These data, indicating reaction on every collision, are considered within the context of detailed work that has been described hitherto following the production of ³¹Si derived from nuclear recoil in the presence of buta-1,3-diene and involving ring formation, and in relation to the reaction of (CH₃)₂Si: with but-2-yne in steady pyrolysis investigations.