Concentration measurements in CO/N 2 and Ar/N 2 gas mixtures using femtosecond coherent anti-stokes Raman scattering
Conference Paper
Overview
Overview
abstract
Single-laser-shot concentration measurements in CO/N 2 and Ar/N 2 gaseous mixtures are performed using femtosecond (fs) coherent anti-Stokes Raman scattering (CARS) with a chirped probe pulse. Measurements are performed in a heated gas cell at temperatures of 300, 600, and 900 K for the complete range of binary gas mixtures. Due to the broadband nature of the ultrafast pulses, Raman transitions of CO (2145 cm -1) and N 2 (2330 cm -1) are probed simultaneously. A theoretical model is developed to extract temperature and concentration measurements from the experimental data. The best agreement between theory and experiment was found for probe-pulse time delays from 0 to 2 picoseconds (ps). Preliminary concentration measurement results are promising when the lasers are tuned to the minor species Raman transition frequency. Measurements performed in Ar/N 2 mixtures are used to explore detection limits in environments with strong nonresonant backgrounds. Experimental data is also reported utilizing polarization suppression of the nonresonant background and further analysis will be performed in the future. These measurements will help to determine the effect of resonant and nonresonant gases on temperature measurements based on the N 2 spectral shape. Copyright 2011 by the American Institute of Aeronautics and Astronautics, Inc.
