Characterization of the electrosprays of 1-ethyl-3-methylimidazolium bis„trifluoromethylsulfonyl... imide in vacuum

The electrosprays of 1-ethyl-3-methylimidazolium bis trifluoromethylsulfonyl imide are composed of a complex mixture of ions and charged droplets, which can be analyzed to determine the structure of the beam and infer significant features of the electrohydrodynamic atomization. In particular, we use a combination of retarding potential and time of flight techniques to study these beams and are able to quantify the voltage drop along the cone jet, together with the velocity and diameter of the jet at the breakup location, confirm the strong influence of viscosity and electrification in the breakup, show that the electric field in and near the Taylor cone tip is insensitive to external electrostatic parameters, and study the spatial distribution of ions and droplets, whereby the paradoxical absence of ions in the outmost region of the beam is established. The research described in this article can be exploited in the modeling of capillary instability of charged jets: testing the results of these models is difficult, especially when nanojets are involved, and our findings and techniques provide the experimental support required by the theoretical activity. The present research is also applicable to the modeling of colloid thruster beams. © 2008 American Institute of Physics. DOI: 10.1063/1.2899658