Abstract
The effect of surface impurities on the thermal accommodation coefficient, which is a measure of the energy exchange between a beam of gas atoms and a solid, is studied with a one‐dimensional model. Quantum theory is used to obtain an expression for this coefficient as a function of temperature, mass of the lattice atoms, mass of the impurity atom, force constant associated with the coupling of the lattice atoms to each other, and force constant associated with the coupling of the impurity to the lattice. The conditions under which a localized mode, due to the presence of the impurity, can contribute strongly to the energy exchange are examined. Results are considered in connection with the accommodation coefficient of helium on metals with surface impurities.

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