engleski

Multiphonon atom-surface scattering in the collision system He-Cu(001)

Recent measurements [1] of the angular distributions and time-of-flight spectra of monoenergetic He atom beams scattered from a clean Cu(001) surface under multiphonon conditions (incident He atom energy 100 meV, surface temperature between 100 and 1000 K) were interpreted by using the Glauber-van Hove approach to neutron scattering by crystal lattices conveniently adapted to atom-surface collision problems. From this the authors have drawn a number of conclusions regarding the properties of inelastic He-surface interactions in general, and the values of the interaction parameters which would be specific to multiphonon scattering in the system studied in particular. Here we comment on the limitations of such an approximate treatment and show that an alternative approach, based on the calculation of the multiphonon scattering spectra in the exponentiated Born approximation, which preserves optical theorem, gives better agreement between experiment and theory upon using interaction parameters consistent with the one-phonon scattering spectra. This implies that, regarding the interaction parameters, there exists a smooth transition between the one- and multiphonon scattering regimes.

atom-solid interactions ; scattering ; diffraction ; copper ; low index crystal surfaces ; phonons

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