Observations of atomic emissions from the Io plasma torus and previously published laboratory work suggest that proton collisions with SO2 may be a source of some of the spectral lines. We present an analysis of Balmer series lines seen in the spectra of collisions of protons with SO2 over the range of 50 to 250 keV. Absolute emission cross sections for these lines are measured to be on the order of 10-19 cm2 and are in rough agreement with a parametric model for electron capture which supports charge-transfer ionization of the SO2 target.