Diffusion of hydrogen in rare gas solids: Neutral H atoms and H⁺ protons

In this letter we review and compare the available information about the stability and spectroscopy of the hydrogen atoms and protons in rare-gas solids. Mechanism of the H⁺ diffusion involving protonated rare-gas dimer Rg₂H⁺ formation in the lattice is discussed. We suggest that the puzzling differences in their behavior and the stability are due to the fact that diffusion of hydrogen atoms is thermally activated, while that of the protons is activated by vibrational excitation of the Rg₂H ⁺ under ambient temperature blackbody radiation.