Coherent Anti-Stokes Raman Spectroscopy of Water Vapor for Combustion Diagnostics

Abstract

The coherent anti-Stokes Raman spectroscopy spectrum of H2O has been measured in a heated optical cell and in laboratory flames. Comparisons of the experimental spectra with a theoretical model have been used to infer information about the unknown Raman linewidths of H2O. In the test cell, excellent agreement has been obtained between theory and experiment in terms of physically realistic linewidths. Agreement between experiment and theory in laboratory flames is also good.

Application of the rotational diffusion model to the CARS spectra of high‐temperature, high‐pressure water vapour

“…Using a constant linewidth model [TI = PI?,( T ) ] and fitting pressure, also slightly improved the sum of squares and inferred ro( T ) to be 45% of that in Ref. 9. However, in each case the improvement in fit was not statistically significant.…”

“…In this case B = 0.0821, V, = 0.0 and the value V,( T ) was then set equal to that in Ref. 9, which is the only source of temperature-dependent linewidth data. Least-squares fitting, To( T ) , reduced the value to approximately 60% of that in Ref.…”

“…Least-squares fitting, To( T ) , reduced the value to approximately 60% of that in Ref. 9. Using a constant linewidth model [TI = PI?,( T ) ] and fitting pressure, also slightly improved the sum of squares and inferred ro( T ) to be 45% of that in Ref.…”

Pure rotational Coherent anti‐Stokes Raman spectroscopy of water vapor and its relevance for combustion diagnostics

“…already in 1979. Measurements in a wider range of conditions were performed by Hall et al . and Greenhalgh et al .…”

“…[18] The first vibrational CARS spectra of the gas phase of water were recorded by Hall et al [19] already in 1979. Measurements in a wider range of conditions were performed by Hall et al [20] and Greenhalgh et al [21] to study the suitability of the technique for combustion applications. The technique has subsequently been successfully applied in different combustion situations.…”