Experimental studies of the formation of cluster ions formed by corona discharge in an atmosphere containing SO2, NH3, and H2O

•We observe charged clusters containing more than 100 water molecules.•Only clusters with a maximum of two sulfuric acid molecules were observed.•The negative ion HSO5− was found to be contaminated by O2−(HNO3)(H2O) ions.•An unidentified ion with m/z = 232 capable of attaching H2O-molecules was observed.

We report on studies of ion-induced nucleation in a corona discharge taking place in an atmosphere containing SO2, NH3, and H2O at standard temperature and pressure. Positive ions such as H3O+(H2O)n, NH4+(H2O)n, and H+(H2SO4)(H2O)n and negative ions such as HSO5−(H2O)n, SO4−(H2O)n, HSO4−(H2O)n and NO3−(H2O)n have been recorded. Large values of n (>100) were observed and the experiment indicates the existence of even larger water clusters. In contrast, only clusters with a maximum of 2 sulfuric acid molecules were observed. Fragmentation studies also revealed that the negative ion HSO5−, which has been observed in many studies, in our experiments is contaminated by O2−(HNO3)(H2O) ions, and this may also have been the case in other experiments. Finally an ion with m/z = 232 (where m is the cluster mass in amu and z is the charge state), capable of attaching H2O-molecules was observed and studied by fragmentation.

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