Dissociative excitation of SO2 by electron impact

Dissociative excitation of SO2 by electron impact to produce excited oxygen fragments, in particular O (1S), has been studied in the energy range from threshold to 400 eV. Three processes leading to O (1S) production have been identified and the positions of the relevant repulsive states of SO2 in the Franck-Condon region have been determined. The multiplicities and symmetry characteristics of two of these states have also been established. The absolute cross section for production of O (1S) by all channels is measured to be 2.2 x 10^-18 cm^2 at 150 eV. The relative cross section for production of 0 (3p 3P and 3p 5P) from threshold to 400 eV has also been measured. The existence of a hitherto unidentified triplet state of SO2 that emits in the near infra red has been established.