IMPURITY TRAPPING EFFECTS IN THE LOCALIZATION OF MUONS IN SOLIDS

Muon spin rotation ( mu SR) experiments are now regularly used to study solids and solid-state processes. The interpretation of mu SR data is usually based on a 'standard' picture in which the muons localise randomly in the solid, and then diffuse, possibly encountering impurities. There remain some important cases where no satisfactory interpretation results. For some of these anomalous systems the authors propose an alternative picture in which the two different factors are the importance of metastable (free muon) excited states, and the role of impurities in causing localisation. They show this allows a possible explanation of results for Al:Mn and demonstrate that elastic strain fields of defects may be a major factor in influencing localisation. They also propose a new mechanism for delayed self-trapping

Perspectives on information and supply chains within investment banking

Supply chain concepts are usually confined to industries where there are core sourcing, manufacture and delivery processes. These industries are usually to be found within the industrial products, aerospace, automotive, chemical and pharmaceutical sectors. Supply Chain Management (SCM) concepts, have not necessarily been associated with financial services, apart from concepts of information management and process flow, in the loosest sense. This paper attempts to describe how supply chain concepts are very much an inherent part of the financial services process landscape, with particular reference to the field of investment banking. In doing so, the paper explores IT/IS issues impacting within the investment banking industry, focussing on the requirements for efficient distribution of sales and research data. Following this, the authors extend concepts of supply chain and information management, to realise the concept of an Investment Banking Information Supply Chain (IBISC)

ELECTRONIC-STRUCTURE OF SELF-TRAPPED EXCITON IN SODIUM-CHLORIDE

The electronic structure of the relaxed exciton is investigated using a Hartree-Fock method. The model concentrates on a cluster of two sodium and two chlorine ions surrounded by an array of point charges. The excited states of the exciton and the associated transitions are discussed. The results are compared with experiment and with the phenomenological models proposed earlier workers. A number of features are confirmed, giving a general picture close to that of Kabler and his co-workers. One problem emerges, since it proves possible to understand the sigma luminescence or the pi luminescence, but not both at present. Possible reasons are discussed. In other respects, there is good agreement with experiment, especially for the optical transitions starting from the lowest triplet state of the exciton

Making tracks in metals

Swift heavy ions lose energy primarily by inelastic electronic scattering and, above an energy threshold, electronic losses result in damage to the lattice. Such high energy radiation is beyond the range of validity of traditional cascade simulations, and predictive damage calculations are challenging. We use a novel methodology, which combines molecular dynamics with a consistent treatment of electronic energy transport and redistribution to the lattice, to model how swift heavy ions form damage tracks. We consider a range of material parameters (electron-phonon coupling strength, thermal conductivity and electronic specific heat) and show how these affect the maximum lattice temperature reached and the extent of residual damage. Our analysis also suggests that fission tracks may form in alloys of archaeological interest

The challenges of nanostructures for theory

It is tempting to believe that modelling in nanotechnology is much the same as that for conventional solid-state physics. However, important areas of nanotechnology address different systems. The mechanics of DNA (for instance) resembles spaghetti more than silicon, the statistical physics needed is often not carrier statistics, and the role of viscosity (the low Reynolds number limit) is not always the familiar one. The idea of equilibrium may be irrelevant, as the kinetics of nonequilibrium (perhaps quasi-steady state) can be crucial. Even when the issues are limited to nanoscale structures (rather than functions), there is a complex range of ideas. Some features, like elasticity and electrostatic energies, have clear macroscopic analogies, but different questions emerge, such as the accuracy of self-organisation. Others concepts like epitaxy and templating are usually micro- or mesostructural. Some of the ideas, which emerge in modelling for the nanoscale, suggest parallels between molecular motors and recombination enhanced diffusion in semiconductors. (C) 2002 Elsevier Science B.V. All rights reserved

DEFECT MIGRATION IN SOLIDS - MICROSCOPIC CALCULATION OF DIFFUSION RATES

Diffusion includes some of the commonest processes on an atomic scale, in which uncorrelated atomic jumps bring about changes in solids. The many predictions of activation energies characterising the temperature dependence of diffusion have high accuracy when good interatomic potentials are known, and a continually improving accuracy from direct quantal calculations. Much more is needed to find the absolute rate at some temperatures. Recent work for both classical and quantum diffusion shows that rates too can be estimated with respectable accuracy. Such calculations highlight basic problems of solid-state defect physics. They alsow offer predictions of techonogical value for diffusion rates in cases where the timescale or physical conditions are too hard for direct experiment. This talk will discuss (a) various ways of obtaining absolute rates, (b) rates of cation diffusion in oxides and their for the so-called Compensation rule (c) issues of charge state in oxides and semiconductors or the motion of shortlived species, and (e) quantum diffusion of hydrogen in metals