High precision measurement of spectroscopic parameters of H₂S in 6320—6350 cm^–1 band

Abstract

As a highly corrosive and highly toxic gas, hydrogen sulfide (H<sub>2</sub>S) is an important intermediate product or pollutant in many fields such as chemical industry, energy and environment. Accurate online measurement of its concentration is of great significance for process control and production safety. Tunable diode laser absorption spectroscopy (TDLAS), as a quantitative absorption spectroscopy technique, is suitable for high-precision on-line measurement of H<sub>2</sub>S concentration in atmospheric environment and industrial processes. Considering that most of the spectroscopic parameters of H<sub>2</sub>S in the HITRAN2020 database are mainly calculated based on semi-empirical theoretical model and lack of experimental data verification, in this paper, direct absorption spectroscopy (DAS) method was firstly used to measure the absorption spectra of H<sub>2</sub>S in the band of 6320~6350 cm<sup>-1</sup>. Six groups of characteristic lines with strong absorption and relative independence were selected as the target transitions for experimental measurement. Then, the wavelength modulation-direct absorption (WM-DAS) method with no calibration and high signal-to-noise ratio was used to measure the absorbances of the six groups of transitions under different pressures. Voigt, Raution and quadratic speed-dependent Voigt profiles were least squares fit to the measured absorbances in order to obtaining the spectroscopic parameters such as the collision broadening coefficient, line strength and Dicke narrowing coefficient, and the minimum standard deviation of residual error of absorbances was 7×10<sup>-5</sup>. The measurement uncertainty of line strengths were less than 2%, and the uncertainty of collision broadening coefficients, Dicke narrowing coefficients and the speed-dependent coefficients were less than 10%. This work is helpful to improve the H<sub>2</sub>S spectral database and provide the spectral data basis for the high-precision measurement of H<sub>2</sub>S concentration.