Laser-induced emission spectrum from high-temperature silica-generating flames

High-temperature silica-generating flames were probed with 266 nm plane, linearly polarized light to produce laser-induced emission spectra with prominent peaks at the blue- and red-shifted sides from the probe wavelength. The radiation induced is ascribed to silicon monoxide (SiO) present in the flame, and appears to be caused by a combination of fluorescence and near-resonance-enhanced Raman scattering. The signal contribution due to strongly depolarized radiation near the probe wavelength complicates extraction of size information based on Rayleigh- and Mie-scattering in investigations of silica nanoparticle formation and growth in flames where temperatures are above 2000 K, oxygen partial pressures are moderate and the particulate matter is in its early stages of evolution. However, the observed radiative process may have utility as the basis for temporally and spatially resolved species and temperature diagnostics.