We report on the production and study of stable, highly charged droplets of superfluid helium. Using a novel experimental setup we produce neutral beams of liquid helium nanodroplets containing millions of atoms or more that can be ionized by electron impact, mass-per-charge selected, and ionized a second time before being analyzed. Droplets containing up to 55 net positive charges are identified and the appearance sizes of multiply charge droplets are determined as a function of charge state. We show that the droplets are stable on the millisecond time scale of the experiment and decay through the loss of small charged clusters, not through symmetric Coulomb explosions.

A high sensitivity, high resolution tandem mass spectrometer to research low-energy, reactive ion-surface interactions Review of Scientific Instruments 91, 065101 (2020);

Features of the solvation of Cs+ by H2 or D2 are unveiled by means of a combined experimental and computational work.

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The detectiono fm ultiply charged helium droplet anions is reported for the first time. By ionizing droplets of superfluid helium with low energy electrons (up to 25 eV), it was possible to produce droplets containing up to five negative charges, which remaini ntact on the timescale of the experiment.T he appearance sizes for differentc harge states are determined and are found to be orders of magnitude largert han for the equivalentc ationic droplets, starting at 4 millionH ea toms for dianions. Droplets with He* À as charge carriers show signs of being metastable, but this effect is quenched by the pickup of water molecules.