A study of the absolute photoabsorption, photoionisation and photodissociation cross sections and the photoionisation quantum efficiency of sulphur dioxide from the ionisation threshold to 400 Å Original Research Article

The absolute photoabsorption, photoionisation and photodissociation cross sections and the photoionisation quantum efficiency of sulphur dioxide have been measured using a double ion chamber and monochromated synchrotron radiation. The absorption spectrum exhibits extensive vibrational structure extending from the ionisation threshold to approximately 750 Å. Many of the features can be arranged into vibrational progressions with spacings characteristic of the symmetrical stretching mode, in agreement with previous interpretations. The photoionisation quantum efficiency increases rapidly to reach a value of approximately unity around 880 Å, but at shorter wavelengths local minima are observed around 760, 820 and 870 Å. Some of the variations in the photoionisation quantum efficiency appear to be correlated with the absorption vibrational structure. A sum rule analysis has been carried out by combining the present absolute photoabsorption measurements with similar data covering the remaining wavelength regions.