Authors: GB Rieker X Liu H Li JB Jeffries RK Hanson
Publish Date: 2006/12/14
Volume: 87, Issue: 1, Pages: 169-178
Abstract
Tunable diode lasers TDLs are used to measure high resolution 01 cm1 nearinfrared NIR water vapor absorption spectra at 700 K and pressures up to 30 atm within a highpressure and temperature optical cell in a highuniformity tube furnace Both direct absorption and wavelength modulation with second harmonic detection WMS2f spectra are obtained for 6 cm1 regions near 7204 cm1 and 7435 cm1 Direct absorption measurements at 700 K and 10 atm are compared with simulations using spectral parameters from HITRAN and a hybrid database combining HITRAN with measured spectral constants for transitions in the two target spectral regions The hybrid database reduces RMS error between the simulation and the measurements by 45 for the 7204 cm1 region and 28 for the 7435 cm1 region At pressures above 10 atm the breakdown of the impact approximation inherent to the Lorentzian line shape model becomes apparent in the direct absorption spectra and measured results are in agreement with model results and trends at elevated temperatures reported in the literature The wavelengthmodulation spectra are shown to be less affected by the breakdown of the impact approximation and measurements agree well with the hybrid database predictions to higher pressures 30 atm
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