  We report on the characterization of a superconducting nanowire detector for
ions at low kinetic energies. We measure the absolute single particle detection
efficiency $\eta$ and trace its increase with energy up to $\eta = 100$ %. We
discuss the influence of noble gas adsorbates on the cryogenic surface and
analyze their relevance for the detection of slow massive particles. We apply a
recent model for the hot spot formation to the incidence of atomic ions at
energies between 0.2-1 keV. We suggest how the differences observed for photons
and atoms or molecules can be related to the surface condition of the detector
and we propose that the restoration of proper surface conditions may open a new
avenue to SSPD-based optical spectroscopy on molecules and nanoparticles.
