Measurement of O2 and O3 absorption cross-sections in the 180–270 nm by controlling the conversion of O2 to O3 in the linear-absorption region

Abstract

Oxygen (O₂) and ozone (O₃) are of crucial importance to human health and environmental sustainability. Concentrations of O₂ and O₃ can be measured by UV absorption spectroscopy, in which the absorption cross-section (ACS) is a very critical physical parameter for calculating concentrations. However, the existing ACS of O₂ and O₃ are biased because the conversion of O₂ to O₃ and nonlinear effects in absorption are ignored in the measurement of ACS. In this study, the ACS for O₂ and O₃ are obtained by considering the conversion of O₂ to O₃ and the nonlinear effects. First, the conversion of O₂ to O₃ is inhibited by controlling gas flow rate and light intensity in the measurement of O₂ and O₃ ACS. Then the concentration of O₃ is indirectly calculated by controlling conversion of O₂ to O₃ during the measurement of ACS of O₃. Next, the linear-absorption regions for O₂ and O₃ are determined by constructing the relationship between absorption intensities and concentrations to eliminate the influence of nonlinear effect. The maximum ACS for oxygen and ozone are $7.84\times {10}^{-20}$ cm²/molecule ($\lambda$ = 180.51 nm) and $1.32\times {10}^{-17}$ cm²/molecule ($\lambda$ = 255.39 nm) by controlling conversion of O₂ to O₃ in the linear-absorption region, respectively.