ABSTRACT
Interactions between gas-phase ions of opposite polarities occur commonly in various environments such as the atmosphere, plasmas, ames [1-4], etc. It has been more than a century since the rst study of the interaction between oppositely-charged ions, which can be dated back to the work by Thomson and Rutherford [5]. However, the study of ion/ion reactions can be challenging particularly when the reactions take place between singly-charged cations and anions, as was the case in the majority of the early studies, because the products are neutral species and, therefore, difcult to analyze and detect. With the advent of electrospray ionization (ESI) [6-9] and its propensity for producing multiply-charged ions from high mass molecules, attention has been directed to the reactions between oppositely-charged ions involving multiply-charged ions, which produce charged products readily amenable to study by mass spectrometry. Consequently, a rapidly-growing range of reaction phenomena are being observed in the ion/ion reactions of multiply-charged ions, which is permitting new insights to be drawn regarding ion/ion reaction thermodynamics and dynamics. While ion/ion
reactions involving large multiply-charged ions are not important in plasmas or ames, for example, they are enabling an expanding array of new analytical applications, particularly in bioanalysis.
