Combined Vibrational and Rotational CARS for Simultaneous Measurements of Temperature and Concentrations of Fuel, Oxygen, and Nitrogen
Simultaneous measurements of temperature and relative concentrations of fuel, oxygen, and nitrogen using combined vibrational coherent anti-Stokes Raman Spectroscopy (CARS) and dual-broad-band rotational CARS have been demonstrated with the use of a Nd:YAG laser and a single dye laser. With the use of a double-folded BOXCARS phase-matching scheme, both the vibrational and the rotational CARS signals were generated in such a way that the signals were superimposed at the spectrograph. With an additional mirror arrangement inside the spectrograph, both signals were recorded simultaneously on a single diode-array detector. The accuracy of single-shot fuel concentration measurements has been investigated, and measurements in a methane/air diffusion flame have been demonstrated. The influence of systematic errors on measured concentrations is discussed.