# What is the minimum and maximum limit for Hydrogen Adsorption distance?

In chemical adsorption of H$_{2}$ molecule, the distance is limited. In the physical adsorption, the distance of adsorption is limited or can be any value? Is there any correspondence to adsorption distance with the van der Waals radius of the adsorbent and adsorbate?. Is there experimental measurements for the minimum and maximum limit for the H$_{2}$ adsorption distance?

As far as I know, the potential energy of the molecule could be minimum at a distance of approximately one molecular radius of the adsorbate. The energy minimum is in the order of something like $0.01–0.1\ \mathrm{eV}=1–10\ \mathrm{kJ\;mol^{-1}}$. Due to the weakness of the interaction, significant changes are only observed at low temperatures ($<273\ \mathrm{K}$).