Temperature determination of superheated water vapor by rotational-vibrational Raman spectroscopy.

We present a novel non-invasive laser-based tool for tracer-free spatially resolved temperature measurement in superheated water vapor at atmospheric pressure. The technique exploits the temperature sensitivity of the rotational-vibrational Raman spectrum of the nu(1) stretching vibration. This Letter demonstrates the Raman sensor, its application to a steam gasification reactor, and four methods to analyze the Raman spectra in order to obtain the temperature: an equal intensity point approach, a pseudo-isosbestic point approach, and two approaches based on the reconstruction of the Raman band by Gaussian/Lorentzian profiles. The evaluated water vapor temperatures inside a reactor for plasma-assisted gasification are compared to data acquired by supercontinuum absorption spectroscopy. (C) 2018 Optical Society of America