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 (H₂S) 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 H₂S concentration in atmospheric environmental monitoring and industrial processes control. Considering that most of the spectroscopic parameters of H₂S in the HITRAN2020 database are mainly calculated based on semi-empirical theoretical model and the experimental data to support them are lacking. In this work, direct absorption spectroscopy (DAS) method is firstly used to measure the absorption spectra of H₂S in the band of 6320–6350 cm^–1. Six groups of characteristic lines with strong absorption and relative independence are 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 is used to measure the absorbances of the six groups of transitions under different pressures. Voigt, Raution and quadratic speed-dependent Voigt profiles fit the measured absorbances by least squares method in order to obtain 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 is 7×10^–5. The measurement uncertainty of each line strength is less than 2%, and the uncertainty of collision broadening coefficients, Dicke narrowing coefficients and the speed-dependent coefficients are all less than 10%. This work is helpful in improving the H₂S spectral database and providing the spectral data basis for the high-precision measurement of H₂S concentration.