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

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(1) A(u) - X (1)A(g) and a (3)A(u) - X (1)A(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 glyoxat 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.htmi or email request to the authors. (c) 2004 Elsevier B.V. All rights reserved.