A study was made of the atomic surface diffusion, at low temperatures, of Cr adatoms deposited onto Cu(100), Cu(111) and Au(111) surfaces. Time-dependent X-ray magnetic circular dichroism, Monte Carlo simulations, and the Kimball-Shortley iterative method were used to evidence a mechanism of quantum tunneling involved in the Cr adatom surface diffusion at below 40K. It was shown that the X-ray magnetic circular dichroism line shape was correlated to the atomic configuration of Cr deposited on a metallic surface. A diffusion rate ranging from 0.03Hz for Cu(100) to 30Hz for Au(111) at 10K was reported from the time evolution of the X-ray magnetic circular dichroism line shape. A quantum equation of motion for the Cr adatom was derived and solved by using a Kimball-Shortley iterative method. Good agreement between the calculated Bohr periods and the experimental diffusion rates was reported.

Low-Temperature Surface Diffusion on Metallic Surfaces. H.Bulou, F.Scheurer, C.Boeglin, P.Ohresser, S.Stanescu, E.Gaudry: Journal of Physical Chemistry C, 2009, 113[11], 4461-7