Trapping and Energy Transfer in Atomic Collisions with a Crystal Surface. II. Impurities

Abstract

The influence of surface impurities and internal impurities on (1) atomic condensation on a solid, (2) equilibration of the newly captured atom with the solid, and (3) the accommodation coefficient, are examined through calculations with a one‐dimensional semi‐infinite analog in the harmonic approximation. The general equation for the semi‐infinite lattice (arbitrary composition) and impinging gas atom are specialized to (1) a pure lattice with a surface impurity (variable mass and bonding) and (2) a pure lattice with a defective third atom (variable mass and bonding). For the surface impurity: a decrease in coupling K₁ decreases the condensation efficiency. Decreasing either the mass M₁ or K₁ decreases the rate of thermalization of a captured atom. There is a maximum in the condensation efficiency when M₁ is varied. Light surface atoms do increase the accommodation coefficient. For the internal impurity: a weakening of impurity bonding decreases both trapping efficiency and rate of thermalization. Light impurities decrease the condensation efficiency, but increase the thermalization rate. The effect of the internal impurity on the accommodation coefficient is negligible.