It was noted that, as well as the desorption and surface trapping of selectively excited guest atoms at the surface of rare-gas solids that were doped with a rare gas, a new relaxation mechanism had been observed. It involved the surface diffusion of long-lived atomic-type surface centers, and guest-molecule formation at the surface. It was analyzed by means of time-resolved and spectrally-resolved luminescence measurements. The desorption of excited atoms, and the existence of weakly-bound surface centers was studied in detail and was simulated by means of molecular dynamics calculations. The rare-gas solids were particularly suitable for investigating these processes because guest atoms at the surface could be selectively excited with tunable vacuum ultra-violet radiation.

M.Runne, I.Reimand, G.Zimmerer: Materials Science Forum, 1997, 239-241, 667-70