A mass spectrometric study of ions extracted from point to plane DC corona discharge fed by carbon dioxide at atmospheric pressure

Mass spectra of the negative ions formed in both positive and negative corona discharges using carbon dioxide as the feed gas containing traces of water (around 50 ppm) operating at atmospheric pressure were analysed. Most of the ions detected were in the form of clusters containing large numbers of water molecules. Discharges operated with a positive polarity contain H3O+·(H2O)n clusters. In contrast an analysis of a negative corona discharge operating at atmospheric pressure and room temperature shows much more complex anionic spectra with five groups of ions and theirs clusters, having the relative yields close to 10% and higher, being observed (CO3−, CO4−, O2−, HCO3−, and HCO4−). The relative yield of each type of ions is found to be strongly affected by the discharge current. Mechanisms for the formation of such ionic species are discussed in detail.