Raman and resonance fluorescence spectra, determined by inelastic light scattering measurements, are used to identify molecular species and to measure their concentration gradients on a fine spatial scale throughout a CVD reactor. Raman spectra are also analyzed to give gas temperature and tempetature profiles. The temperature profiles near the leading edge of a horizontal rf heated susceptor in a laminar flow system are adequately described by using Lévêque's solution to an energy balance equation, assuming temperature-independent fluid properties. Raman spectra at room temperature of some of the compounds commonly used as source materials for Si epitaxial growth, SiCl4, SiCl3H, SiCl2H2 and Si2Cl6 indicate that these species are all detectable at the 10-100 ppm level and are distinguishable from each other. Measurements at 500-1300°C of these compounds reveal the presence of a common species, SiClx (probably SiCl2), which exhibits a resonance flourescence spectrum at least 1000 times more intense than typical Raman spectra. SiClx density profile measurements above the susceptor indicate a concentration boundary layer thickness of 0.7-0.8 cm for one set of experimental conditions. SiClx density measurements as a function of suspector temperature are observed to vary over a range of 4 to 5 orders of magnitude, and are much higher for a SiCl2H2 input than for a SiCl4 input. © 1975.