Time-dependent solvation of potassium ions in helium nanodroplets: Interaction fingerprints

Alkali atoms that tend to reside at the surface of helium droplets become gradually solvated and embedded inside the droplets upon ionization. Recent laser experiments have monitored this process in real time, employing another dopant (xenon atom) whose ionization triggers Coulomb ejection of the partially solvated sodium cation. In this article we have carried out a complete atomistic modeling of the pump-probe double ionization process, in the case of potassium and in comparison with earlier similar modeling carried out for sodium [J. Chem. Phys. 161, 121101 (2024)]. While the phenomenology remains essentially the same for both alkalis, the weaker interaction between the droplet and the neutral potassium atom relative to sodium, despite the interaction in the ionic state being at least as strong, gives rise to delayed and slower solvation. Unlike with sodium, Coulomb ejection from the fully solvated K+Xe non-covalent complex is predicted to produce the ejection of both partially solvated ions, leaving a bare helium droplet behind.