High temperature investigations of methane for the calculation of the temperature dependence of spectral parameters

Lengden, Michael and Johnstone, Walter and Bain, James Roderic Peter and Milne, Laura (2011) High temperature investigations of methane for the calculation of the temperature dependence of spectral parameters. In: 8th International Conference on Tunable Diode Laser Spectroscopy, 2011-07-11 - 2011-07-15. (Unpublished)

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Abstract

For gas sensing applications in high temperature environments, such as aeroengine exhaust, solid oxide fuel cells and flames, it is important to have accurate knowledge of the temperature dependence of the spectral parameters used for laser gas composition measurements. Here we present methane spectral measurements for a number of spectral manifolds, taken using direct tunable diode laser spectroscopy, for a temperature range of 50-850°C. The R(4) manifold is of particular interest in this work, as the individual transition assignments vary between the HITRAN2008 database [1], based on the work of Frankenberg [2], and the GOSAT database [3]. Comparative spectra will be shown using parameters from both databases, as will temperature dependence calculations for the self- and nitrogen-broadening parameters. Studies of the R(4) manifold have previously been carried out at high temperatures [4], however, only the HITRAN transitional assignments were used. Furthermore, two ‘hot’ lines have been found in the R(4) manifold that are not present in the work of Gharavi and Buckley [4]. This is because they interrogated a much smaller wavelength range in their work, as they were operating at pressures of ~0.1 bar compared to the atmospheric pressure measurements taken in this work. We provide linestrength and position values for these new transitions.

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