Ion–surface scattering reveals unexpected oscillations

A series of ion‐surface scattering studies has revealed surprising oscillatory cross sections that some atomic physicists are hailing as macroscopic evidence of quantum‐mechanical phase interference phenomena. Robert Erickson and David Smith (Central Research Laboratories, 3M Company, St. Paul) saw the pronounced regularly spaced oscillations when they measured scattering cross sections as a function of primary energy for the elastic scattering of lowenergy noble‐gas ions from a number of solid surfaces. Although similar oscillations are well known in ionic collisions in gases, this is the first report of such oscillations in scattering from surfaces. Erickson and Smith explain their results in terms of binary collisions (as in a gas) between an incident ion and a surface atom, and a resulting quasimolecular state with shared electrons. Although not everyone is satisfied that the experimental data are yet sufficient to rule out other likely explanations, most agree that the results are exciting if this interpretation is borne out.

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