Measurement of the absorption cross-sections of sulfur compounds in the 180–270 nm region considering nonlinear effects

Abstract

Sulfur compounds (SO₂, CS₂, H₂S and OCS) are common toxic pollutants in the atmospheric environment, and the absorption spectroscopy technique can indeed help to realize online monitoring of their concentrations. However, nonlinear effects that occur during absorption spectroscopy measurements have a serious impact on the measurement of the absorption cross-sections (ACSs) of sulfur compounds, leading to serious deviations in both the substance absorption properties and concentrations obtained based on ACS analysis. In this paper, the maximum effective ACSs of sulfur compounds in the linear region are obtained by considering the influence of nonlinear effects and eliminating interference factors such as oxygen and photolysis. In addition, the nonlinear effects are found to be greatly attenuated in spectra with broad band absorption characteristics by comparing the oscillatory absorption spectra before and after the differential treatment and by comparing the change in the oscillatory ACS with the broad band ACS. The experimental results show that the effective ACSs of SO₂, CS₂, H₂S, and OCS with a resolution of 0.23 nm are 14.15 × 10⁻¹⁸ cm² per molecule, 5.61 × 10⁻¹⁶ cm² per molecule, 7.09 × 10⁻¹⁸ cm² per molecule, and 3.20 × 10⁻¹⁹ cm² per molecule, respectively. So far, it is the largest ACS obtained at room temperature and atmospheric pressure, which is of great significance for online measurement of sulfur compounds.