Temperature dependent determination of the S-branch Raman linewidths of oxygen and carbon dioxide in an oxyfuel relevant mixture.

Abstract

The temperature dependence of the ${\\rm O}_2$ and ${\\rm CO}_2$ S-branch linewidths in a 30/70% ${\\rm O}_2 - {\\rm CO}_2$ mixture between 295 K and 1900 K has been studied by a picosecond time-resolved pure rotational coherent anti-Stokes Raman scattering (RCARS) approach. The S-branch Raman linewidths are required for diagnostics of thermodynamic properties in oxyfuel combustion processes by RCARS, where this mixture is of special interest, because it is regularly used to replace air when transiting from air-fed to oxyfuel combustion. The obtained linewidths for oxygen and carbon dioxide show a strong deviation from pure self-broadened linewidths and previously used Q-branch linewidths, respectively. A discussion on the expected impact on RCARS thermometry and concentration evaluations as well as a description of specific properties of oxygen and carbon dioxide and their effect on the dephasing behavior of the Raman coherences and, thereby the Raman linewidths, is included, along tabulated linewidths data of both molecules.