He beam scattering and leed evidence for partial facetting of a Pt(997) surface

Partial facetting of a Pt(997) surface is obtained by high temperature annealing in oxygen. The facets produce a characteristic, very sharp peak in the He scattering pattern. The ability of He scattering to evidence even a relatively small amount of facets is proven. LEED patterns obtained with grazing primary beam also show the simultaneous presence of facets and undisturbed stepped regions. The lack of evidence for the presence of facets in the LEED patterns obtained at normal incidence is discussed.     

Observation of sputtering damage on Au(111)

The morphology of a Au(111) surface has been observed with the STM (scanning tunneling microscope) after ion bombardment with 2.5 keV Ne⁺ ions at about 400 K. Mostly triangular and hexagonal shaped vacancy islands are seen in the STM topographs. They are bounded by monatomic steps, oriented along the closed packed 110 directions. The general morphology confirms the conclusions inferred from TEAS (thermal energy atom scattering) measurements on ion bombarded Pt(111) surfaces. The observation of a propensity for the formation of {100} microfacetted 110 ledges is discussed.     

Dynamical parameters of desorbing molecules

The aim to uncover fundamental details of the desorption process as well as the needs of more applied research, like fusion, led recently to a growing interest in the study of the parameters of desorbing molecules. The main experimental methods and the most significant experimental results obtained so far are reviewed and discussed. The investigation of the parameters of desorbing molecules being one of the oldest fields of surface science, a number of pre- and misconceptions still hamper the mutual understanding and hereby impede progress. Accordingly, a relatively large pace is dedicated to the historical development, to definitions, and even to semantics.     

Coadsorption of NO and D2 on Rh(100)

The question addressed in the title was investigated experimentally for low coverage CO and H on Pt(111). The consistent result of two kinds of experiments is that the scattering cross section is in general not influenced by the surface temperature, except for H on Pt(111) in the limit of small changes of the normal component of the He wave vector, Δ k_z. The result simplifies substantially the use of He scattering as an analytical technique for surface dynamics investigations. Semi-classical arguments indicate that the lack of influence of the surface temperature at low coverages is related to two circumstances: (1) the small contribution to the specular He beam of the scattering from adsorbate induced disturbances of the repulsive potential and (2) the absence of long range modifications of the vibrational properties of Pt induced by adsorbed CO or H.     

Three-dimensional numerical simulation of the reciprocating flow in a branching tube network

The paper deals with the three dimensional numerical simulation of the reciprocating flow in a branching network, a phenomenon that might be found for example in the human bronchi. As the first approximation, the working fluid was water with laminar flow regime. The main issue was to elucidate the mechanism of the air exchange in the human lungs. The model used in this simulation consists of two branching generations. Three different cases have been analyzed with various frequency, Re and Wo numbers.