Vibrationally excited SiO has been observed in the 193 nm photolysis of N2O
/SiH4 mixtures with and without great excess of H-2. While SiH4 + O(D-1) (1
) has been known to produce SiO in the mixture without H-2, present kinetic
analyses of SiO and OH indicate that SiH3 + OH (2) is responsible for the
SiO production in the mixture with H-2. The observed nascent vibrational di
stributions, approximated by Boltzmann distributions of T-v = 5200 +/- 660
K for (1) and 2800 +/- 790 K for (2), are reasonably accounted for by a sta
tistical model assuming multi-step unimolecular decomposition of hot silano
l.