Concurrent processes in the time-resolved solvation and Coulomb ejection of sodium ions in helium nanodroplets

Abstract

Recent pump-probe experiments [Albrechtsen {\em et al.}, Nature {\bf 623}, 319 (2023)] have explored the gradual solvation of sodium cations in contact with helium nanodroplets, using a fully solvated xenon atom as a probe exerting a repulsive interaction after its own ionization. In this Communication we computationally examine by means of atomistic ring-polymer molecular dynamics the mechanisms of successive ionizations, shell formation, and Coulomb ejection that all take place within tens of picoseconds, and show that their interplay subtly depends on the time delay between the two ionizations but also on the droplet size. The possibility of forming solvated Na$^+$Xe non-covalent complexes under a few tens of picoseconds in such experiments is ruled out based on fragment distributions.