Kinetics of the initiation step of the thermal decomposition of SiCl₄

The initiation reaction of the thermal decomposition of silicon tetrachloride SiCl₄ + M →k_l SiCl₃ + Cl + M (R1) was studied behind reflected shock waves at temperatures between 1550 K and 2370 K and pressures between 1 and 1.5 bar. Atomic resonance absorption spectrometry (ARAS) was applied for time-resolved measurements of H atoms at the L_α-line in SiCl₄/H₂/Ar systems. Additional experiments were performed in the SiCl₄/Ar system following the absorption of SiCl₄ at the L_α -line. Rate coefficients for the reaction (R1) were determined to be: k_l = 4.8 × 10¹⁶exp(-40954 K/T) cm³mol^-1s^-1 The choice between two possible alternatives of the first decomposition step, namely elimination of either Cl₂ or Cl has been made in favor of the second reaction on the basis of ki- netic and energetic considerations.