Spectroscopic studies of planetary atmospheres and high-temperature processes (e.g., combustion) require absorption line-shape models that are accurate over extended temperature ranges. To date, advanced line shapes, like the speed-dependent Voigt and Rautian profiles, have not been tested above room temperature with broadband spectrometers. We investigate pure water vapor spectra from 296 to 1305 K acquired with a dual-frequency comb spectrometer spanning from 6800 to $7200\mathrm{c}{\mathrm{m}}^{-1}$ at a point spacing of $0.0033\mathrm{c}{\mathrm{m}}^{-1}$ and absolute frequency accuracy of $<3.3\times {10}^{-6}\mathrm{c}{\mathrm{m}}^{-1}$. Using a multispectral fitting analysis, we show that only the speed-dependent Voigt accurately models this temperature range with a single power-law temperature-scaling exponent for the broadening coefficients. Only the data from the analysis using this profile fall within theoretical predictions, suggesting that this mechanism captures the dominant narrowing physics for these high-temperature conditions.

• Received 14 June 2017

DOI:https://doi.org/10.1103/PhysRevA.96.022514