The Atom - Surface Interaction in Physisorption.

The atom-surface interaction in physisorption was studied from both theoretical and experimental standpoints. The experimental work, i.e., atomic beam scattering of helium atoms from the diamond (111) surface, resulted in the first successful measurement of bound state resonances and diffraction patterns. From these data energy levels for the laterally -averaged He-C (diamond) potential and the modulation or corrugation of the potential on the surface were obtained. The reconstruction of the diamond (111) surface was studied using both atom beam scattering and LEED techniques. The temperature at which the reconstruction took place and the periodicity of the new surface agreed with other LEED studies. In the theoretical work values of the coefficient C(,3) of the long range part of the atom-surface interaction were calculated for many systems. There values are of interest in experiments of atom beam scattering from surfaces and adsorption isotherms. A simple formula for C(,3) was also obtained which permits one to obtain C(,3) values using a few physical parameters. A hypothesis of universal behaviour in physical adsorption was formulated and checked with experimental data from atom beam scattering experiments. This law, analogous to corresponding states laws valid in the bulk, predicts that all atom-surface systems have a common potential when suitable reduced units are introduced. Experimental data confirm that there is a common trend, but upon closer examination, consistent differences show up for different substrates (for example, insulators vs. metals). Other studies carried out included calculations of the modification of the adatom-adatom interaction due to the presence of a surface and the calculation of the short range part of the atom-surface interaction.