Measurement of the dissociation rates of ion clusters in ionic liquid ion sources
Catherine E. Miller, Paulo Lozano
Abstract
Ionic liquid ion sources utilize electric fields to evaporate and accelerate ions and ion clusters to ∼1 keV energies. Ion clusters may dissociate after evaporation, which is not a well-characterized phenomenon and has relevant consequences in many applications. We measure the dissociation rate-constants of ion clusters for several ionic liquids. It is found that ion cluster dissociation occurs on timescales of the order of 1–5 μs and follows a constant-rate equation in the region outside the ion source. Using the measured rate-constants, we estimate the post-emission ion cluster temperatures. We also qualify the way the electric field enhances the rate-constants. Finally, our work supports the hypothesis that ion clusters with many degrees of freedom have lower dissociation rates.