Raman lidar system for methane gas concentration measurements

Ultraviolet Raman-scattering measurements in flames by the use of a narrow-band XeCl excimer laser

Spectra with simultaneous peaks of CO(2), O(2), N(2), CH(4), and H(2)O are taken by the use of spontaneous Raman scattering from free jets and a turbulent CH4 diffusion flame. A narrow-band XeCl excimer laser working at 308 nm and an intensified multichannel camera are used to give full information about all major species and the spectral background. Knowledge of the structure of the background is important for data analysis. For O(2), an enhancement that is due to near-resonant Raman scattering is found. Assuming no influence of this enhancement on the temperature dependence of the O(2) Raman-scattering cross section, temperature and concentrations of all major molecules are determined simultaneously from the intensity of the Raman bands. Experimental details and a data reduction scheme based on the analysis of the entire spectral shape are reported. Strong fluorescence backgrounds from OH radicals found in the high-temperature regions of the flame are discussed.