Figures and show part of the effect of hydration due to the limited inclusion of water in the clusters. It can be seen that the effect of varying the relative humidity between 34% and 73% is a modest factor of 2, which is negligible compared to the changes in the cluster formation potential rate due to changes in IA concentration. Therefore, the direct effect of hydration of these clusters is not significant. However, in this study we neglect the hydrolysis reaction of the oxide clusters, which have been shown to be reactive with water both experimentally and theoretically. The hydrolysis reactions, shown in reaction R1 and R2, will lead to a conversion of oxide clusters into oxyacid-water clusters, which has been shown to have a reaction barrier for IP of 7.7 kcal mol -1 56