Interaction of neutral hydrogen atoms with KCl(001)

Neutral hydrogen atoms with velocity selected thermal energies, have been scattered from KCl(001) cleavage planes in UHV. For cold crystal surfaces (Tsub(SF) <= 710 K) even a small residual pressure of water resulted in an ordered monolayer coverage of the (001) plane. From this surface, diffraction has been observed with diffracted beams up to third order and characteristically varying intensities were observed and analysed in terms of a quantum mechanical rainbow scattering theory. Resonant transitions of atoms to bound states at the surface ('selective adsorption') were observed and used to determine the interaction potential of hydrogen atoms with this water covered surface: first in terms of a Morse potential, second in terms of a C3/z3-dependent attractive potential. The surface Debye-Waller factor has been measured for clean KCl(001), for the water covered (001) plane as well as for partially covered surfaces. The results are interpreted within a simple model. (Auth.)