CO₂-broadened coefficients of water vapor molecule in 1.1 μm band

Abstract

The absorption spectral parameters of water vapor molecules are the key basic scientific data for the remote sensing detection and the planetary observation applications. Based on a narrow line-width external cavity diode laser and a long-path absorption cell, 18 absorption spectral lines of CO₂-broadened water vapor molecules in a 9332–9722 cm^–1 range at room temperature are measured. To obtain the CO₂-broadened water vapor molecule coefficients, the Voigt profile and the quadratic speed-dependent Voigt profile are used to fit the absorption spectrum data. The quadratic speed-dependent Voigt profile shows better fitting capability. Comparing with the air-broadened coefficients of the corresponding region from the HITRAN2020 database, the mean ratios of the CO₂-broadened coefficients of water vapor molecules and the air-broadened coefficients obtained from the two models of the line shape are 1.327 and 1.454, respectively, which verifies that the method of estimating the CO₂-broadened coefficient by the air-broadened coefficient of water vapor molecules has certain reliability. This study can provide reference data of measured spectral parameters for the detection technology and related research of atmospheric structures of Mars and Venus in the near-infrared region.