Study of energy transfer in helium atom scattering from surfaces

Recently developed quantum mechanical theory of inelastic He atom scattering (HAS) from solid surfaces is employed to analyze the energy transfer between projectile particles (thermal energy He-atoms) and vibrational degrees of freedom (phonons) characteristic of a variety of experimentally studied surfaces. We have first calculated the angular resolved energy transfer which can be directly compared with the values deducible from the HAS time-of-flight spectra and a good agreement with experimental data has been found. This enabled us to calculate the total or angular integrated energy transfer, which is of paramount importance in the studies of gas-surface scattering, but is neither accessible in HAS (which yields only the angular resolved quantities), nor in the wind tunnel measurements for surfaces whose atomic composition and cleanliness must be maintained during the experiment. Here we present the results for prototype collision systems of this kind, viz. He => Cu(001), He => Xe/Cu(111) and He => Xe(111) which are representative of the very different types of surface vibrational dynamics and thereby provide an insight into some common properties of energy transfer in gas-surface scattering.