The surface properties of rare gas crystals have been explored using a He molecular beam as the dynamical probe. Specifically, ordered monolayer, bilayer, trilayer, and bulk Ar, Kr, and Xe were grown on an Ag(111) substrate). This has allowed us to examine how the physical properties of these films evolve on a layer by layer basis. Elastic diffraction and selective adsorption experiments were used to investigate the He-surface interaction potential. Comparing the results of close-coupled calculations with the experimental data, both the laterally averaged potential and higher order terms in the energy expansion can be determined. To examine the dynamical properties of the adsorbed rare gases, angle and time resolved inelastic scattering was used. This technique made it possible to investigate the dynamics of the surface across the entire Brillouin zone. In this paper on the properties of Ar(111) multilayers are specifically examined. These data are compared to the theoretical calculations of several other groups, testing the validity of several model potentials, and the importance of various interaction terms when constructing these potentials. Originator supplied keywords include: Surface phonon spectroscopy; phonon dispersion curves; surface dynamics; thin films; inelastic single phonon scattering; physisorption interactions; gas-surface energy exchange; rare gas interaction potentials.

This report reviews experiments involving He scattering from the surfaces of ordered rare gas overlayers physisorbed on Ag(111). The series of rare gases studied were Ar, Kr, and Xe. The measurements were performed on thin film structures which were grown on a layer-by-layer basis, from monolayer to thick film, in order to study how the surface properties changed with increasing distance from the substrate. Three types of experiments are discussed; elastic diffraction, selective adsorption, and inelastic single phonon scattering by angle-resolved time-of-flight. These experiments, taken together, provide a broad overview of the static and dynamic surface properties of rare gas overlayers. They also provide information about the forces which govern the adatom-adatom and adatom-substrate interactions. Originator supplied keywords include: Surface phonon dispersion relations; Helium diffraction; Selective adsorption; Rare gas interaction potentials; Thin film dynamics; Gas-surface energy exchange; Wetting.

Research involving the chemical physics of the inert or rare gases continues unabated. This small volume is meant to deal with advances that have occurred in three selected areas over the past decade. It forms a natural outgrowth of earlier reviews and volumes that have dealt almost exclusively with pure rare-gas solids. Originally, a single chapter was envisaged to cover the topic of alloys and impurities in solid rare gases. However, over the past ten years this single chapter spawned many offshoots and eventually the project became too large for a single volume. Thus the present book contains only a small subset of possbile topics involving rare-gas solids intentionally doped with impurities. Chapter 1 gives a brief overview of current research devoted to the rare gases. This is followed by a comprehensive, self-contained chapter dealing with the most recent developments in the area of interatomic inter actions. Chapter 3 is concerned with the lattice dynamics of rare-gas solids doped with an impurity which is either another rare-gas or a small molecule. The final chapter deals with the spectroscopy of vibrating and rotating di atomic impurities in rare-gas solids. The birth of this volume was not without its labour pains. I should like to take this opportunity to thank the various people who have at one time or another been involved throughout its gestation period. Clearly, many important topics are omitted from this volume.

Experimental advances in helium atom scattering spectroscopy over the last forty years have allowed the measurement of surface phonon dispersion curves of more than 200 different crystal surfaces and overlayers of insulators, semiconductors and metals. The first part of the book presents, at a tutorial level, the fundamental concepts and methods in surface lattice dynamics, and the theory of atom-surface interaction and inelastic scattering in their various approximations, up to the recent electron-phonon theory of helium atom scattering from conducting surfaces. The second part of the book, after introducing the experimentalist to He-atom spectrometers and the rich phenomenology of helium atom scattering from corrugated surfaces, illustrates the most significant experimental results on the surface phonon dispersion curves of various classes of insulators, semiconductors, metals, layered crystals, topological insulators, complex surfaces, adsorbates, ultra-thin films and clusters. The great potential of helium atom scattering for the study of atomic scale diffusion, THz surface collective excitations, including acoustic surface plasmons, and the future prospects of helium atom scattering are presented in the concluding chapters. The book will be valuable reading for all researchers and graduate students interested in dynamical processes at surfaces.