TIME-RESOLVED LMR MEASUREMENT OF THE RATE CONSTANTS OF THE REACTIONS SIH3+SIH3 AND SIH3+CL

The kinetics of the reactions SiH3 + SiH3 and SiH3 + Cl were studied using time-resolved laser magnetic resonance (LMR). The silyl radical arising in KrF laser (248 nm) photolysis of SiH4/COCl2/Ar mixture was detected. The rate constants obtained from the decay kinetics of SiH3 signals at T = 295 are k1(SiH3 + SiH3) = (1.6 +/- 0.5) X 10(-11) cm3/s and k2(SiH3 + Cl) = (3.2 +/- 1.0) X 10(-11) cm3/s. The values of k1 and k2 were found to be unchanged under variation in argon pressure from 6 to 17.3 Torr. The other rate constants measured and estimated are k3(SiH4 + Cl) = (2.5 +/- 0.5) X 10(-10) CM3/s, k4(SiH3 + CO) less-than-or-equal-to 7 X 19(-16) cm3/s, k5(SiH3 + HCI) less-than-or-equal-to (1.8 +/- 0.5) X 10(-15) cm3/S, k6(SiH3 + COCl2) less-than-or-equal-to 5 X 10(-15) cm3/s and k7(SiH3 + NF3) less-than-or-equal-to 5 X 10(-15) cm3/S. Possible reasons for the lower rate constants of hydrogen atom abstraction by chlorine atom for the reaction involving SiH3 compared to that for the reaction with the molecule SiH4 are discussed. It is assumed that in collision SiH3 and Cl species are oriented so that the probability of their approach in the configuration favourable for the abstraction reaction decreases.