We present a model for quantitative measurements in binary mixtures of nitrogen and carbon monoxide by the use of dual-broadband rotational coherent anti-Stokes Raman spectroscopy. The model has been compared with experimental rotational coherent anti-Stokes Raman scattering spectra recorded within the temperature range of 294–702 K. Temperatures and concentrations were evaluated by spectral fits using libraries of theoretically calculated spectra. The relative error of the temperature measurements was 1–2%, and the absolute error of the CO concentration measurements was <0.5% for temperatures ≤600 K. For higher temperatures, the gas composition was not chemically stable, and we observed a conversion of CO to CO2. The influence of important spectroscopic parameters such as the anisotropic polarizability and Raman line-broadening coefficients are discussed in terms of concentration measurements. In particular, it is shown that the CO concentration measurement was more accurate if N2-CO and CO-N2 line-broadening coefficients were included in the calculation. The applicability of the model for quantitative flame measurements is demonstrated by measuring CO concentrations in ethylene/air flames.
© 2004 Optical Society of America
(280.1740) Remote sensing and sensors : Combustion diagnostics
(280.2470) Remote sensing and sensors : Flames
(300.6170) Spectroscopy : Spectra
(300.6230) Spectroscopy : Spectroscopy, coherent anti-Stokes Raman scattering
Mikael Afzelius, Christian Brackmann, Fredrik Vestin, and Per-Erik Bengtsson, "Pure Rotational Coherent Anti-Stokes Raman Spectroscopy in Mixtures of CO and N2," Appl. Opt. 43, 6664-6672 (2004)