Electron Collisions With Molecules Clusters And Surfaces

This volume contains the invited papers and selected contributed papers presented at the biennial International Symposium on ELECTRON COLLISIONS WITH MOLECULES, CLUSTERS AND SURF ACES held at Royal Holloway, University of London from 29th to 30th July, 1993. This Symposium was a Satellite Meeting of the XVIII International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC) and follows a 16 year tradition of Satellite Conferences in related areas of collisions held in association with previous ICPEAC's. In the past each of these electron -molecule symposia covered the broad field of electron-molecule scattering at rather low energies, but also included hot topics. This time as well as covering the whole field, well defined electron collisions with clusters and with particles in the complex potential of a surface were emphasized. Not many details are known about such collisions, although they become more and more important in surface characterisation, plasma-wall interactions, electron induced desorption and reorganisation of adsorbed particles. Recently, much work, theoretical and experimental, has been devoted to electron collisions with rather large carbon, silicon and halogen containing molecules. These problems are of relevance in plasma assisted thin film formation and etching of surfaces and can now be approached with advanced theoretical methods and experimental equipment.

Since the early days of modem physics spectroscopic techniques have been employed as a powerful tool to assess existing theoretical models and to uncover novel phenomena that promote the development of new concepts. Conventionally, the system to be probed is prepared in a well-defined state. Upon a controlled perturbation one measures then the spectrum of a single particle (electron, photon, etc.) emitted from the probe. The analysis of this single particle spectrum yields a wealth of important information on the properties of the system, such as optical and magnetic behaviour. Therefore, such analysis is nowadays a standard tool to investigate and characterize a variety of materials. However, it was clear at a very early stage that real physical compounds consist of many coupled particles that may be excited simultaneously in response to an external perturbation. Yet, the simultaneous (coincident) detection of two or more excited species proved to be a serious technical obstacle, in particular for extended electronic systems such as surfaces. In recent years, however, coincidence techniques have progressed so far as to image the multi-particle excitation spectrum in an impressive detail. Correspondingly, many-body theoretical concepts have been put forward to interpret the experimental findings and to direct future experimental research. This book gives a snapshot of the present status of multi-particle coincidence studies both from a theoretical and an experimental point of view. It also includes selected topical review articles that highlight the achievements and the power of coincident techniques.

Research on photon and electron collisions with atomic and molecular targets and their ions has seen a rapid increase in interest, both experimentally and theoretically, in recent years. This is partly because these processes provide an ideal means of investigating the dynamics of many particle systems at a fundamental level and partly because their detailed understanding is required in many other fields, particularly astrophysics, plasma physics and controlled thermonuclear fusion, laser physics, atmospheric processes, isotope separation, radiation physics and chemistry and surface science. In recent years a number of important advances have been made, both on the experimental side and on the theoretical side. On the experimental side these include absolute measurements of cross sections, experiments using coincidence techniques, the use of polarised beams and targets, the development of very high energy resolution electron beams, the use of synchrotron radiation sources and ion storage rings, the study of laser assisted atomic collisions, the interaction of super-intense lasers with atoms and molecules and the increasing number of studies using positron beams.

Professor Philip G. Burke, CBE, FRS formally retired on 30 September 1998. To recognise this occasion some of his colleagues, friends, and former students decided to hold a conference in his honour and to present this volume as a dedication to his enormous contribution to the theoretical atomic physics community. The conference and this volume of the invited talks reflect very closely those areas with which he has mostly been asso- ated and his influence internationally on the development of atomic physics coupled with a parallel growth in supercomputing. Phil’s wide range of interests include electron-atom/molecule collisions, scattering of photons and electrons by molecules adsorbed on surfaces, collisions involving oriented and chiral molecules, and the development of non-perturbative methods for studying multiphoton processes. His devel- ment of the theory associated with such processes has enabled important advances to be made in our understanding of the associated physics, the interpretation of experimental data, has been invaluable in application to fusion processes, and the study of astrophysical plasmas (observed by both ground- and space-based telescopes). We therefore offer this volume as our token of affection and respect to Philip G. Burke, with the hope that it may also fill a gap in the literature in these important fields.

Since the turn of the 21st century, the field of electron molecule collisions has undergone a renaissance. The importance of such collisions in applications from radiation chemistry to astrochemistry has flowered, and their role in industrial processes such as plasma technology and lighting are vital to the advancement of next generation devices. F

Numerous experiments and calculations have shown that isolated metal clusters possess many interesting features, quite different from those known from surface and solid- state physics or from atomic and molecular physics. The technological exploitation of these new properties, e.g. in miniature electronic or mechanical components, requires the cluster to be brought into an environment such as an encapsulating matrix or a surface. Due to the interaction with the contact medium, the properties of the clusters may change or even disappear. Thus the physics of cluster-on-surface systems -- the main subject of this book -- is of fundamental importance. The book addresses a wide audience, from the newcomer to the expert. Starting from fundamental concepts of adsorbate-surface interactions, the modification of electronic properties through electron confinement, and concepts of cluster production, it elucidates the distinct properties of the new metallic nanostructures.

This proceedings volume contains the invited talks presented at two atomic physics symposia held jointly in Buenos Aires, Argentina from 28-30 July 2005. All papers were peer-reviewed. They represent the latest research in dynamics of collision systems involving collisions between photons, electrons, and ions and a diverse range of target species: atoms, molecules, clusters, and surfaces. There is a particular emphasis on correlation and many-body effects in excitation and ionization.