Localization and Delocalization of a Single Molecule in a Helium Nanodroplet

When embedded in superfluid helium nanodroplets, the dopant molecule exhibits either localization or delocalization behaviors that are critically determined by the spatial spread of its wave function, which in turn are influenced by the confining potential of the nanodroplets. Here, we examine the spatial extent of a molecule's wave function with respect to the size of the nanodroplet by diagnosing the angular nodal structures in the photoelectron momentum distributions (PMDs). We find that, for the lightest H2 molecules or heavier D2 and O2 molecules, with extents of wave function distributions comparable to or smaller than the nanodroplet size, the emitted electrons undergo either minimal or significant scattering with the liquid helium surroundings, leading to either preserved or blurred nodal structures in the PMDs. These observations reveal the underlying delocalization or localization of a molecule within the nanodroplet, which is governed by its wave functions as determined by the confining potential of the droplet. Our findings provide insight into the quantum solvation dynamics of light impurities in nanoscale and confined systems.