Ethane thermometry using rotational coherent anti-Stokes Raman scattering (CARS)

The complete rotational CARS (coherent anti-Stokes Raman scattering) spectrum of ethane (C2H6) has for the first time been recorded instantaneously under high spectral resolution, and the potential for thermometry has been investigated. Experiments were performed in the temperature range 292-650 K in pure ethane and in binary mixtures with nitrogen. A polarization technique was used to suppress the non-resonant contribution to the CARS signal. The ethane RCARS spectra show both S-and R-branch lines, which are more closely spaced than for the well-known nitrogen spectrum and located at much smaller Raman shifts. The peak signal strength was found to be around 240 times lower for ethane than for nitrogen (at 292 K). Two main approaches for ethane thermometry are evaluated, which both show high potential. The first is a method in which a spectrum with unknown temperature is fitted using a library of experimental spectra recorded at various temperatures. The second is a method based on ratios of integrated signals in different spectral regions. A theoretical model for simulation of theoretical spectra is under development. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.