High-resolution photoabsorption cross-section measurements of SO2 at 295 Kbetween 198 and 220 nm

SO2 is an important constituent of the atmospheres of Io and Venus. Accurat e photoabsorption cross-section data at the temperatures of these planetary atmospheres are required for the interpretation of SO2 observations and fo r reliable photochemical models. As part of a planned series of measurement s over the 160-300 K range, photoabsorption cross sections of SO2 at 295 K, in the wavelength region 198-220 nm, have been determined from very high r esolution (resolving power (lambda/Delta lambda) approximate to 450,000) ab sorption spectra recorded with a vacuum ultraviolet Fourier transform spect rometer. These new measurements are compared with earlier, lower-resolution (lambda/Delta lambda approximate to 100,000) photoabsorption measurements at 213 K spanning the same wavelength region, with lower-resolution (lambda /Delta lambda approximate to 100,000) measurements at 295 K in a more limit ed region, and with a recent Doppler-limited laser diode measurement at 295 K over a very narrow wavelength region.