Temperature and concentration measurements in acetylene-nitrogen mixtures in the range 300-600 K using dual-broadband rotational CARS

Purl rotational coherent anti-Stokes Raman scattering (CARS) experiments ha ve been performed in acetylene for temperatures ranging from 294 to 582 K, and in mixtures of acetylene and nitrogen in the mole fraction range of 0.0 6-0.32 for acetylene at room temperature. The experimental spectra are eval uated by a least-square fitting to libraries of theoretically calculated sp ectra using two different Raman linewidth models, one with and one without dependence on the rotational quantum number J. It is found that a J-depende nt model is favourable, both regarding temperature measurements in pure ace tylene, and simultaneous acetylene concentration and temperature measuremen ts in different mixtures of acetylene and nitrogen. For the temperature mea surements performed in pure acetylene the temperature inaccuracy is general ly less than 2% when the J-dependent model for the Raman linewidths is used . It is found that fitting the value of the nan-resonant susceptibility sig nificantly improves the quality of the spectral fits and is a requirement f or high temperature accuracy with the present model. The evaluated concentr ations show a maximum error of 13% on a relative scale. Potential sources o f systematical errors both regarding measured temperatures and acetylene co ncentrations are discussed.