Abstract

Absolute concentration measurements of trace species using laser-induced fluorescence provide a sensitive test of the chemical mechanism of reactive processes. These absolute measurements require spectroscopic data for the measured species, knowledge of the fluorescence quantum yield for the specific excited state of that species, a measurement of the gas temperature of the process, and a calibration of the sensitivity of the optical collection and detection. Demonstration measurements of LIF absolute concentrations of OH and NO in a low pressure air flame and OH in a diamond CVD plasma are described. Each of these measurements relies on a different calibration technique, and the advantages of each of these methods are discussed. Direct and indirect determinations of the quantum yield are used, and the difficulties of these measurements are considered. The care required for spatially correlated gas temperature determination is elucidated.

© 1992 Optical Society of America