Multiple ionization of pristine HNDs distributes charge centers in minimum energy configurations close to the surface of the droplets where they form a 2D-Wigner crystal. Dopants are polarized and attracted by these charge centers which leads to a homogeneous growth of singly-charged clusters and nanoparticles with an unprecedentedly narrow size distribution. These dopant cluster ions can be removed from the large host droplets still solvated with up to a few 100 He atoms via splashing of the HND upon surface collisions or controlled shrinking in a helium buffer gas.
Splashing of doped helium droplets leads predominantly to backscattering of embedded dopant clusters. However, by taking advantage of this effect, it is possible to cover surfaces within seconds with a film of monodisperse clusters or nanoparticles