Modulated transmission spectroscopy of gaseous chemi-excited Ca and Sr monoxides

Abstract

Low pressure dilute diffusion flames of the metal-oxidation (M + N(2)O) and chain reaction (M + N(2)O + CO) types have been studied in absorption by means of modulated intracavity resonance spectroscopy. The measurements obtained were comparable in sensitivity to the intracavity dye laser technique but were of lower spectral resolution. The modulation experiment which is described herein has the advantage of measuring linearly and in real time the transmission factor gamma free from adverse anomalous dispersion effects. It is therefore well suited to the determination of electronic state densities. In these measurements, theground states of CaO and SrO were not detected, but the excited (1)pi and (3)pi states absorbed measurably and as a function of CO content in the flames.