High-resolution absorption cross-section of glyoxal in the UV–vis and IR spectral ranges

Abstract

High-resolution absorption cross-sections of glyoxal have been recorded at 296 K in the ultraviolet and visible (UV–vis: 19000–40000 cm −1, 250–526 nm) and infrared (IR: 1200–8000 cm −1) spectral ranges by means of a Fourier transform spectrometer (FTS). The UV–vis spectra were measured at 1 atm of N 2 bath gas. The spectral resolution of the FTS was selected to be 0.06 cm −1 for the richly structured A ˜ 1A u – X ˜ 1A g and a ˜ 3A u – X ˜ 1A g band systems, and 1 cm −1 for the diffuse B ˜ − X ˜ transition, which was sufficient to resolve most spectral structures. In addition, low and high-resolution IR spectra (1 and 0.009 cm −1 spectral resolution) of glyoxal/N 2 mixtures were recorded around 2835 cm −1 at 0.2 mbar, 100 mbar, 300 mbar and 1 atm total pressure. UV–vis and IR spectra were recorded quasi-simultaneously by making sequential measurements of identical glyoxal mixtures in the cell, enabling the direct comparison of UV–vis and IR spectral parameters for the first time. The high-resolution spectra have been used to simulate deviations from Lambert–Beer's law, which occur at lower resolution when spectra are not fully resolved. Special attention has been paid to reduce the uncertainty of the UV–vis spectrum, allowing for an improved determination of the atmospheric photolysis of glyoxal. Finally, the new UV–vis spectrum has been used to redetermine our previous DOAS measurements of glyoxal yields from the reactions of OH radicals with benzene, toluene and p-xylene. The high-resolution spectral data can be obtained from http://iup.physik.uni-bremen.de/gruppen/molspec/index.html or email request to the authors.