Measurement of the dissociation rates of ion clusters in ionic liquid ion sources

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.