UV-spectra and pressure broadening of SO2, CH2O and CS2.

Absolute and differential absorption cross sections were determined with a cw-dye ring laser (1) to obtain fully resolved molecular spectra. The spectral range of our present experiments covered the important region of the OH-radical absorption around 308 nm (250 GHz range). The many-line spectra and the absorption coefficents of SO2, CH2O and CS2 were investigated. In addition, the pressure broadening of these gases was determined in the range from a pure Doppler broadened spectrum up to atmospheric pressure. The broadening parameter was determined by comparing the broadened spectra with the convolution of the low pressure spectra with a Lorentz function. In addition, the temperature dependance of the SO2 spectrum is determind from room temperature down to minus 70 degree C for a decrease of overlapping spectral structures. These data can be used as reference in long path DOAS experiments to determine tropospheric trace gas concentrations.