Knowledge Bank

Resonance Raman spectroscopy provides a means of selectively detecting and profiling non-fluorescent species in flames. Selectivity of detection is an important pre-requisite for analytical work in combustion because of the myriad of of potential interfering compounds present in flames. By careful choice of excitation wavelength non-fluorescent compounds present in low concentrations can be detected. Interference from background fluorescence of polyaromatic hydrocarbons (PAH) is dramatically reduced by exciting in the far ultraviolet. Emission from PAH molecules begins at -250 nm and extends to longer wavelengths. Excitation at -216 nm leaves a spectral window in which to observe the Raman spectrum. The vibrational Raman spectrum of the target molecule, and species present in high concentration (methane, nitrogen, and water) have been obtained. Results for trichloroethylene, tetrachloroethylene, and benzene in methane flames will be presented