Evaluation of two different gas temperatures and their volumetric fraction from broadband N(2) coherent anti-Stokes Raman spectroscopy spectra

Appl Opt. 1995 Jun 20;34(18):3313-7. doi: 10.1364/AO.34.003313.

Abstract

Technical flames often contain regions of high temperature gradients at a length scale that is smaller than or comparable with the size of the probe volume used. In these situations the coherent anti-Stokes Raman spectroscopy (CARS) signal is composed of contributions of gases of different temperatures. Here a fitting routine is presented that allows the evaluation of the different temperatures that occur in the CARS spectra by splitting the temperature mixed spectra into contributions of two main temperatures. Additionally, the volumetric fraction of both gas components with those two different temperatures can be determined. The evaluation procedure has been tested by the use of measured temperature mixed CARS spectra that have been taken in two gas samples with different gas temperatures.