Laser-induced Fluorescence of Unstable Intermediates in Combustion: HSO and H₂CS

Abstract

Temperature measurement and detection of unstable intermediates are essential in understanding combustion mechanisms in detail. Among many diagnostics, the laser-induced fluorescence (LIF) technique is one of the most useful because of its spectral selectivity, high sensitivity, and spatial resolution. OH, NO, N₂, and H₂ molecules have often been detected by LIF or CARS (Coherent-Anti-Stokes Raman Spectroscopy). Rather complicated tunable ultraviolet lasers or powerful visible lasers are required to detect these simple radicals or molecules by LIF or CARS. If some molecules generated in combustion absorbvisible laser light, they are useful both in simplification of the laser diagnostics system and in reduction of the cost of the laser system. Sulfur-containing molecules especially HSO and H₂CS have their absorption bands in the visible region and are generated in the combustion of sulfur-containing fuels [1]. In this article we describe the use of LIF to study combustion mechanisms involving HSO and H₂CS generated as unstable intermediates during combustion.