  Highly excited states of rubidium (Rb) atoms attached to helium (He)
nanodroplets are studied by two-photon ionization spectroscopy in combination
with electron and ion imaging. Photoion spectra and angular distributions are
in good agreement with a pseudodiatomic model for the RbHe_N complex. Repulsive
interactions in the excited states entail fast dissociation followed by
ionization of free Rb atoms as well as of RbHe and RbHe_2 exciplexes.
Nonresonant excitation generates Rb atoms in low-lying electronic levels by
statistical evaporation-like desorption.
