Adsorption of H$_2$ on Amorphous Solid Water Studied with Molecular
  Dynamics Simulations
  We investigated the behavior of H$_2$, main constituent of the gas phase in
dense clouds, after collision with amorphous solid water (ASW) surfaces, one of
the most abundant chemical species of interstellar ices. We developed a general
framework to study the adsorption dynamics of light species on interstellar
ices. We provide binding energies and their distribution, sticking
probabilities for incident energies between 1 meV and 60 meV, and thermal
sticking coefficients between 10 and 300 K for surface temperatures from 10 to
110 K. We found that the sticking probability depends strongly on the adsorbate
kinetic energy and the surface temperature, but hardly on the angle of
incidence. We observed finite sticking probabilities above the thermal
desorption temperature. Adsorption and thermal desorption should be considered
as separate events with separate time scales. Laboratory results for these
species have shown a gap in the trends attributed to the differently employed
experimental techniques. Our results complement observations and extend them,
increasing the range of gas temperatures under consideration. We plan to employ
our method to study a variety of adsorbates, including radical and charged
species.
