EXPLORATION OF SURFACES BY ATOMIC SCATTERING IN THE ALMOST CLASSICAL REGIME

Inelastic atom-surface scattering at hyperthermal (approximately 1 eV) energies is discussed. In this regime, the scattering is almost classical. However, for a surface at low temperature, peaks in the final energy distribution are broadened by quantum effects. The widths of these peaks provide a direct measure of the zero point motion of the surface atoms. For impulsive collisions, we derive a simple expression for these widths. As an example, we present a semi-quantitative analysis for He striking a LiF surface, using Born-Mayer forces between the atoms to estimate the amplitude of the zero point fluctuations. We discuss, in detail, how single peaks may be isolated in an experiment. Measurements of this effect could provide an important probe of surface dynamics.