Measurements of H2O broadening coefficients of infrared methane lines

Introduction of Water‐Vapor Broadening Parameters and Their Temperature‐Dependent Exponents Into the HITRAN Database: Part I—CO2, N2O, CO, CH4, O2, NH3, and H2S

“…γ H2O for methane. (a) Black circles represent the water‐vapor broadening Lorentz half‐widths of CH 4 in the mid‐infrared and near‐infrared region by (Delahaye et al, ) with the red line for the fourth‐order polynomial fitting (not used in this work), blue triangles from the ν 4 P(5), P(9), and P(10) manifolds by Lübken et al (), and the 2ν 3 R(3) and R(4) manifolds in green diamonds by Gharavi and Buckley (). (b) The ratio of the water‐vapor broadening half‐widths of methane transitions to their corresponding air‐broadening half‐widths in HITRAN, as well as the average value of the those ratios plotted here.…”

“…Although the primary goal of that study was to support Raman thermometry of rocket engines, the authors had extrapolated their data to room temperature values based on the temperature‐dependent exponents fitted from the power law which would be comparable to other spectral regions. In recent years, a few more studies dedicated to water‐vapor broadening parameters of O 2 lines in the pure rotational and A‐band were made by using different techniques: a laser‐based photoacoustic spectrometer (Vess et al, ), a frequency‐multiplier spectrometer with a Zeeman‐modulated absorption cell (Drouin et al, ), a radio‐acoustic detection spectrometer (Koshelev et al, ), and a Fourier transform spectrometer (Delahaye et al, ). In order to provide accurate and reliable spectral parameters for atmospheric applications, the water‐vapor broadening parameters of O 2 lines in the HITRAN database were then divided into two parts for generating the data set.…”

“…In order to provide accurate and reliable spectral parameters for atmospheric applications, the water‐vapor broadening parameters of O 2 lines in the HITRAN database were then divided into two parts for generating the data set. As the first part, γ H2O for O 2 lines in the A‐band were obtained by multiplying air‐broadening coefficients in the A‐band from the HITRAN2016 database by a single scaling factor of 1.1, as per recommendation by the most recent study from Delahaye et al (). For the rest of the transitions, a complete analysis for all collected experimental data (presented in Figure ) was carried out.…”

“…There were an appreciable amount of methane lineshape laboratory studies and theoretical calculations in recent years, but almost all of them were devoted to self-and/or air-broadening line-shape parameters of methane (see for instance, Devi et al, 2015Devi et al, , 2016Ghysels et al, 2014;Hashemi et al, 2015;Smith et al, 2014). The γ H2O parameters for CH 4 transitions in the mid-infrared and near-infrared region were measured recently for the first time using a Fourier Transform spectrometer (Delahaye et al, 2016c). In that study 76 ro-vibrational transitions were measured.…”

Indirect Influence of Humidity on Atmospheric Spectra Near 4 μm

“…This is a good approximation in spectral regions dominated by the contributions of local lines since the pressure-broadening and -shifting coefficients of the transitions of species G (≠ H 2 O) by H 2 O are not so different from those by dry air (e.g., Delahaye et al, 2016aDelahaye et al, , 2016bDelahaye et al, , 2016c. This is a good approximation in spectral regions dominated by the contributions of local lines since the pressure-broadening and -shifting coefficients of the transitions of species G (≠ H 2 O) by H 2 O are not so different from those by dry air (e.g., Delahaye et al, 2016aDelahaye et al, , 2016bDelahaye et al, , 2016c.…”