Narrow Band Phenomena Influence Of Electrons With Both Band And Localized Character

The understanding of electronic behaviour in solids when (some of) the valence electrons have both localized and band-like characteristics is one of the central problems of physics and chemistry in the second half of this century. Many advances have indeed been made using highly sophisticated techniques and concepts. Our objectives in bringing together specialists from different areas was cross-fertilization of ideas and redefinition of bottlenecks and problems. The testimony of the participants and the book which follows indicate a fair degree of success. This book is a record of discussions aimed at digestion and reassessment of some of the recent major advances in our understanding of narrow bands. Note that we expressly asked participants to give a short readable account of the major problems in their field and not to emphasize their latest results to be as "technical" as they might be in a normal scientific article. We did not ask for complete reviews of what was going on in the field and this book should not be read as such. Neither should it be approached as the sort of educational text which the NATO ASI proceedings are supposed to be. We have tried to produce a useable account of a workshop in which an attempt was made to define real problems and to distinguish them from illusory problems.

The Raman Emission by X-rays (REX-I) Workshop focused on Raman Scattering of x-rays mostly from Synchrotron Radiation Sources. The advent of new high brightness sources of x-ray radiation has given new impetus to this tantalizing technique that has offered ways of obtaining new insights into the atomic and electronic structure of solids and gases, but which has been limited by weak sources of excitation. In the last five years, Raman scattering by x-rays has been observed an ubiquitous phenomena. It has been applied to yield new information about the band structure of solids and about the electronic structure of atoms. It was the object of this workshop to identify and define key issues in this rapidly developing subfield of x-ray physics by gathering together a group of theorists and experimentalists, and by providing overlap between atomic and condensed matter physics. The workshop aimed to achieve this end by providing an environment to discuss the latest developments and to initiate cross fertilization in the difference areas. Contents: Radiative and Non-Radiative Resonant Inelastic X-Ray Scattering (T Åberg)The Resonant Raman Scattering and Its Infrared Divergence (J-P Briand)Resonant Soft X-Ray Raman Scattering in Graphite and Hexagonal Boron Nitrite (J A Carslile et al.)Multiplet Effects in Core Level Spectroscopies of Transition Metal Compounds (F M F de Groot)Raman Scattering at Core Exciton of Several Semiconductors (S Shin)Resonant and Non-Resonant Inelastic X-Ray Scattering in Mott-Hubbard Systems (E D Isaacs)Angle Resolved Resonant Raman Auger Spectroscopy on Xe (N Berrah et al.)Resonant Soft X-Ray Emission of Small Molecules (P Skytt et al.)Radiative Raman Scattering by Atoms and Molecules at Ultraviolet Wavelengths (A Dalgarno)X-Ray Parametric Scattering Stimulated by an Intense Laser Field (K Namikawa et al.)and other papers Readership: Physicists and materials scientists keywords:

This volume contains the proceedings of the NATO Advanced Research Workshop on Band Structure Engineering in Semiconductor Microstructures held at Il Ciocco, Castelvecchio Pascali in Tuscany between 10th and 15th April 1988. Research on semiconductor microstructures has expanded rapidly in recent years as a result of developments in the semiconductor growth and device fabrication technologies. The emergence of new semiconductor structures has facilitated a number of approaches to producing systems with certain features in their electronic structure which can lead to useful or interesting properties. The interest in band structure engineering has stimd ated a variety of physical investigations and nove 1 device concepts and the field now exhibits a fascinating interplay betwepn pure physics and device technology. Devices based on microstruc tures are useful vehicles for fundamental studies but also new device ideas require a thorough understanding of the basic physics. Around forty researchers gathered at I1 Ciocco in the Spring of 1988 to discuss band structure engineering in semiconductor microstructures.

The importance of real space imaging and spatially-resolved spectroscopy in many of the most significant problems of surface and interface behaviour is almost self evident. To join the expertise of the tradi tional surface scientist with that of the electron microscopist has however been a slow and difficult process. In the past few years remarkable progress has been achieved, including the development of new techniques of scanning transmission and reflection imaging as well as low energy microscopy, all carried out in greatly improved vacuum conditions. Most astonishing of all has been the advent of the scanning tunneling electron microscope providing atomic resolution in a manner readily compatible with most surface science diagnostic procedures. The problem of beam damage, though often serious, is increasingly well understood so that we can assess the reliability and usefulness of the results which can now be obtained in catalysis studies and a wide range of surface science applications. These new developments and many others in more established surface techniques are all described in this book, based on lectures given at a NATO Advanced Study Institute held in Erice, Sicily, at Easter 1987. It is regretted that a few lectures on low energy electron diffraction and channeling effects could not be included. Fifteen lecturers from seven different Countries and 67 students from 23 Countries and a wide variety of backgrounds attended the school.

This volume contains the papers presented at the NATO Advanced Research Workshop in "Reflection High Energy Electron Diffraction and Reflection Electron Imaging of Surfaces" held at the Koningshof conference center, Veldhoven, the Netherlands, June 15-19, 1987. The main topics of the workshop, Reflection High Energy Electron Diffraction (RHEED) and Reflection Electron Microscopy (REM), have a common basis in the diffraction processes which high energy electrons undergo when they interact with solid surfaces at grazing angles. However, while REM is a new technique developed on the basis of recent advances in transmission electron microscopy, RHEED is an old method in surface crystallography going back to the discovery of electron diffraction in 1927 by Davisson and Germer. Until the development of ultra high vacuum techniques in the 1960's made instruments using slow electrons more accessable, RHEED was the dominating electron diffraction technique. Since then and until recently the method of Low Energy Electron Diffraction (LEED) largely surpassed RHEED in popularity in surface studies. The two methods are closely related of course, each with its own specific advantages. The grazing angle geometry of RHEED has now become a very useful feature because this makes it ideally suited for combination with the thin growth technique of Molecular Beam Epitaxy (MBE). This combination allows in-situ studies of freshly grown and even growing surfaces, opening up new areas of research of both fundamental and technological importance.

The recent generation in the laboratory of phase squeezed and intensity squeezed light beams has brought to fruition the theoretical predictions of such non-classical phenomena which have been made and developed in recent years by a number of workers in the field of quantum optics. A vigorous development is now underway of both theory and experiment and the first measurements have been coi:Jfirmed and extended already in some half dozen laboratories. Although the fields of application of these novellight sources are as yet somewhat hazy in our minds and some inspired thinking is required along these lines, the pace and excitement of the research is very clear. It is to he hoped that the new possibilities of: making measurements below the quantum shot noise lirnit which is made possible by these squeezed states of light willlead to further fundamental advances in the near future. In this NATO ARW a number of the leaders in the field met in the extremely pleasant surroundings of Cortina d'Ampezzo and their contributions are recorded in this volume. The meeting was held at the Istituto d'Arte which was enjoying its lOOth anniversary celebrations. This ARW was preceeded by an ONR Special Seminar on "Photons and Quantum Fluctuations", the proceedings of which will be published by Adam Hilger Ltd. The timeliness of the meeting was acknowledged by the support of the NATO Scientific Affairs Division which we would like to acknowledge on behalf of all the participants.

While its results normally complement the information obtained by chemical experiments, computer computations can in some cases predict unobserved chemical phenomena Electronic-Structure Computational Methods for Large Systems gives readers a simple description of modern electronic-structure techniques. It shows what techniques are pertinent for particular problems in biotechnology and nanotechnology and provides a balanced treatment of topics that teach strengths and weaknesses, appropriate and inappropriate methods. It’s a book that will enhance the your calculating confidence and improve your ability to predict new effects and solve new problems.