Profiles of SiO mole fraction have been obtained in low pressure premixed h
ydrogen/oxygen/hexamethyldisilazane (HMDS) flames by laser-induced fluoresc
ence and emission spectroscopy. SiO is observed to form early in the flame
at temperatures near 1100 K. The flame equivalence ratio has only a small e
ffect on the SiO mole fraction, but the precursor concentration has a marke
d effect on both the peak mole fraction and shape of the profile. The SiO o
bserved in the flame appears to be from two sources: SiO produced directly
from precursor pyrolysis, and SiO that is generated as the partial pressure
from the solid SiO in the flame. A comparison of ground state and excited
state profiles indicates that the emission from SiO is chemiluminescence ra
ther than thermal emission. A computational flow model incorporating curren
t Si/H/O chemical mechanisms is able to qualitatively reproduce some aspect
s of the observed profiles, but significant discrepancies remain. The profi
les presented in this study can serve as a test against which future chemic
al and process models may be validated. (C) 2001 by The Combustion Institut
e.