Showing papers in "Reports on Progress in Physics in 1986"
TL;DR: The physics of pyroelectric detectors is reviewed in this paper, including a discussion of response and electronic noise and their dependence on device design and material parameters, together with techniques for their minimisation.
Abstract: The physics of pyroelectric detectors is reviewed, including a discussion of response and electronic noise and their dependence on device design and material parameters Other sources of noise are described, particularly as generated by environmental effects such as microphony, together with techniques for their minimisation The range of ferroelectric materials which have been assessed for use in pyroelectric detectors is reviewed and their properties compared, particularly from the aspect of application to different types of devices Finally, an account is given of the wide range of applications for which pyroelectric detectors have been used, including a detailed description of both the pyroelectric vidicon and pyroelectric arrays and their application to thermal imagers
883 citations
TL;DR: A general survey of glass transition phenomena and concepts is presented in an introductory section as discussed by the authors, and the physical significance of computer simulations of glass transitions in simple liquids and the question of a hidden phase transition underlying an observed glass transition are examined critically.
Abstract: The different physical aspects of glass transitions are reviewed and models aiming at their explanation are described. The following three main aspects are distinguished: the degree of stability of supercooled liquids with respect to crystallisation; the variation of physical properties of supercooled liquids in metastable equilibrium above the glass transition; the arrest of structural relaxation at the glass transition. The physical significance of computer simulations of glass transitions in simple liquids and the question of a hidden phase transition underlying an observed glass transition are examined critically. In relation to the stability problem, the geometrical constraints operative in typical disordered structures, such as random sphere packings and random covalent networks, are also discussed. A general survey of glass transition phenomena and concepts is presented in an introductory section.
777 citations
TL;DR: In this article, a review of the relations between liquid and solid phase properties across melting for compound systems at stoichiometric composition is presented, and large deviations for stoichiometry can be realised in the liquid phase, to display trends of evolution of structure, bonding and electronic states with composition.
Abstract: Modern techniques of liquid state physics have been successfully used to probe the microscopic structure and dynamics of a variety of multicomponent liquids in which relative ordering of the species is present near freezing. The alkali halides are prototypes for this specific type of short-range order in relation to the nature of bonding, but the systems in question also include other monovalent and polyvalent metal-ion halides, alkali-based intermetallic compounds and chalcogen-based alloys. A viewpoint is taken in this review which gives attention to the relations between liquid and solid phase properties across melting for compound systems at stoichiometric composition. In addition, large deviations for stoichiometry can be realised in the liquid phase, to display trends of evolution of structure, bonding and electronic states with composition.
206 citations
TL;DR: In this paper, the Skyrme model for baryons is introduced and the pion-baryon S-matrix is derived in the adiabatic approximation.
Abstract: The ideas underlying the Skyrme model for baryons are introduced. Applications for the properties of single baryons (B=1) in the case of two and three flavours are based on Skyrme's hedgehog ansatz. The interaction between two baryons is discussed within the product ansatz for the B=2 system. The pion-baryon S-matrix is derived in the adiabatic approximation. The possibility to include quark degrees of freedom is shown in terms of the hybrid model. Finally the origin and implications of the Wess Zumino-Witten action are presented.
154 citations
TL;DR: In this paper, a review of the state of the art in the measurement of thermophysical properties at extreme temperatures can be found, with a focus on self-heating methods.
Abstract: Considerable advances have been made in the measurement of thermophysical properties at extreme temperatures. Traditional static methods have been hampered by chemical interaction of specimens with containers, loss of mechanical strength, etc. Fast dynamic methods have been developed to avoid these difficulties. The present state of development is reviewed. The scope of the review is restricted to self-heating methods and does not include the laser heating techniques such as those used to determine vapour pressure. The systems considered are divided into millisecond and microsecond resolution categories. The slower systems are used primarily in the solid range and are the most mature. The faster systems were developed for measurements in the liquid range where radiation heat losses must be minimised and measurements must be made quickly enough to avoid collapse of the specimen due to gravity. Theoretical equation of state modelling of the measurements and pseudopotential resistivity and thermal expansion calculations are also discussed and a summary of the collected data is given.
134 citations
TL;DR: Ion implantation has been exploited in widely diverse fields both as a powerful research tool for investigating solid state material processes and properties, and as a means of controllably modifying the electrical, physical, chemical, mechanical, mechanical and optical properties of solid surfaces.
Abstract: The incorporation of impurities into solids by bombardment with energetic ions is a non-equilibrium process which can result in intriguing near-surface property changes. This review initially examines the basic ion-solid interaction processes and outlines how such processes can lead to the modification of the composition, structure and surface topography of materials. Ion implantation has been exploited in widely diverse fields both as a powerful research tool for investigating solid state material processes and properties, and as a means of controllably modifying the electrical, physical, chemical, mechanical and optical properties of solid surfaces. These aspects receive major attention in this review which attempts to provide a balanced overview of the impact of ion implantation on solid state science and technology. In particular, special emphasis is given to implantation processes and applications in semiconductors which have received an enormous amount of attention in recent years, stimulated no doubt by the strong technological driving forces within the microelectronics industry. Ion bombardment processes and interesting property changes in metals are also discussed, and a selection of important technological applications is given. Finally, an overview of more recent investigations and applications is presented, including ion implantation into insulators and polymers, insight into crystal growth processes, adhesion of thin films to substrates, and research into ion bombardment of ices which has astrophysical significance.
130 citations
TL;DR: In this article, the authors investigate statistical energy analysis for analyzing the vibrational behavior of complex structures and apply it to sound and vibration transmission in the field of solid-state physics.
Abstract: Theories for analysing the vibrational behaviour of complex structures are examined, parallels being drawn with several other areas of physics in which problems of wave propagation in inhomogeneous media are studied. There are three main stages to the investigation. First, the response to random driving of a single, essentially homogeneous, system is examined. The second, and much more detailed, discussion concerns energy transport between discrete coupled subsystems. In particular, the authors investigate an approach to this problem which is known as statistical energy analysis. The third main topic is the phenomenon of Anderson localisation as it applies to certain problems of sound and vibration transmission-the phenomenon is much better known in the field of solid-state physics. Applications of it to vibration are of interest in themselves, and also shed light on the theoretical basis of statistical energy analysis, which is a diffusive transport theory.
129 citations
TL;DR: In this paper, the most recent studies of rarefied gas flow can be traced back to the early work of Knudsen, who described desorption, evaporation and scattering of molecules from surfaces using the cosine law of scattering.
Abstract: Following a brief historical introduction an overview is given relating the most recent studies of rarefied gas flow to the early work of Knudsen. The first paper submitted in October 1908 (published in 1909) initiated a period of intense activity by Knudsen, Smoluchowski (1910) and, a little later, by Gaede (1913) and Langmuir (1912). This also covered the transition to the already well established hydrodynamic flow expressed in terms of the ratio of mean free path to critical apparatus dimension: which is now referred to as the Knudsen number. The desorption, evaporation and scattering of molecules from surfaces was described in terms of the Knudsen cosine law of scattering. The Knudsen effusion method for determining vapour pressure, also introduced in 1909, has become the main tool for studies of the related problem of the dissociation, chemical bonding and the vaporisation process itself. Clausing (1926) developed, as an alternative to conductances, the concept of transmission probability, still referred to as the Clausing factor, and provided a procedure for their more accurate evaluation in long and short tubes. A number of misconceptions of these early efforts have found their way into the literature and current books on vacuum science and technology. However, detailed studies have clarified the problem of gas-surface interactions; the gas flow in tubes has been tackled with Clausing-type integral equations and by statistical computation techniques based on Monte Carlo analysis procedures adaptable to more complex systems. Results have been confirmed experimentally using molecular-impact pressure probe measuring techniques.
125 citations
TL;DR: In this article, the methods and techniques currently used to measure oscillator strengths (or equivalently, f-values and transition probabilities) are reviewed and both linear and non-linear optical methods are discussed.
Abstract: The methods and techniques currently used to measure oscillator strengths (or, equivalently, f-values and transition probabilities) are reviewed. Both linear and non-linear optical methods are discussed.
119 citations
55 citations
TL;DR: This review examines how this abstraction process of information processing may be dynamically implemented using the concepts of 'chaotic strange attractors' to obtain a Markov chain.
Abstract: Information processing aims at category formation in the (human) cognitive system or the classification of the external (and a good deal of the system's internal) world in a hierarchy of abstract patterns. These patterns in turn may be used as algorithms for simulating observed physical processes. In this review the author examines how this abstraction process may be dynamically implemented using the concepts of 'chaotic strange attractors'. The paper is divided accordingly into three parts. (1) Introduction, where the author deliberates on the physical (hardware) substrate of information and its hierarchical relation to the symbolic (software) aspect; or, more concretely, how from a continuous non-linear dynamics to obtain a Markov chain. (2) Where the dynamics of information generation, compression and dissipation is given. (3) Applications where examples of information processing using the paradigm of chaotic attractors are offered from neurophysiology, cognitive psychology and perception. Finally the author discusses the issue of self-consistency of self-referential linguistic schemes essentially as an eigenvalue problem.
TL;DR: In this paper, a detailed account is given of the formalism of localised electronic states (deep traps or levels) which are produced by substitutional transition metal impurities in III-V semiconductors.
Abstract: A detailed account is given of the formalism of localised electronic states (deep traps or levels) which are produced by substitutional transition metal impurities in III-V semiconductors. The importance of including the two particle Coulomb interactions between the electrons is emphasised throughout. The concepts of bonding is briefly discussed, but the review mainly concentrates on the idea that introducing transition metal impurities results in there being extra, d-like orbitals available to accommodate electrons. These in turn produce 'configurations' and 'terms' similar to those found with free transition metal ions and with the ions in ionic crystals. As with the latter it has been found that a powerful way of accounting for a large amount of experimental information is through the concepts of effective and spin Hamiltonians, with the parameters chosen to agree with experiment. The discussion deals with the question of how such effective forms can be expected to arise.
TL;DR: In this article, the impact of modern surface science techniques on understanding the properties of rare earth metal surfaces is considered, and methods for obtaining and evaluating clean surfaces are critically assessed, and the geometrical and electronic properties of the surface are compared with those of bulk metals.
Abstract: The review considers the impact of modern surface science techniques on understanding the properties of rare earth metal surfaces. Methods for obtaining and evaluating clean surfaces are critically assessed, and the geometrical and electronic properties of the surface are compared with those of bulk metals. Low energy electron diffraction is available on only a limited range of single crystals, but electron spectroscopy has been applied extensively to clean polycrystalline materials. The insights gained imply both a continuation of bulk-like phenomena at the surface (strong exchange and correlation of 4f electrons and of core hole-4f interactions) and intrinsic surface effects such as 4f binding energy shifts, modified surface valence and anomalous surface magnetism.
TL;DR: In this paper, the authors used direct Fourier transform methods to obtain surface structures of adsorbed molecules and molecules on well-characterised surfaces, which can be used for surface crystallographic techniques.
Abstract: Fine structure in photoionisation cross sections for core levels of atoms in molecules and solids can be associated with elastic scattering of the associated photoelectrons and the resulting interference of emitted and scattered components. The measurement of the electronic cross sections is therefore a rich source of structural information on the environment of the absorbing atomic species. For the special case of the study of surfaces, the investigation of extended X-ray absorption fine structure (EXAFS) and near-edge X-ray absorption fine structure (NEXAFS) has led to the development of powerful tools for the investigation of surface structure and particularly of the registry of adsorbed atoms and molecules on well characterised surfaces. EXAFS is dominated by single scattering and with the use of model compounds to eliminate unknown scattering phase shifts, considerable information on surface structures can be obtained using direct Fourier transform methods. These methods are not applicable to other surface crystallographic techniques. Substantial structural information can also be obtained from NEXAFS measurements of adsorbed molecular species without complex modelling calculations, although such calculations are necessary for the interpretation of NEXAFS from atomic adsorbates.
TL;DR: In this article, a review of magnetic bubble domain devices for computer memory, data-flow data processing and optical image processing has been presented, concluding that this is a particularly significant example of the interaction between technology and science.
Abstract: The invention of a number of interesting magnetic bubble domain devices for computer memory, data-flow data processing and optical image processing, has brought many new and interesting problems to the attention of physicists. These problems, in materials, particularly crystal growth, in magnetic domain dynamics, in the physics of ion implantation, in complex magnetic field calculations and in magneto-optics are reviewed and discussed. It is concluded that this is a particularly significant example of the interaction between technology and science.
TL;DR: In this article, the authors review the experimental techniques of neutrino physics, traces the main developments, summarises the present status of the field and gives some hints on future activities.
Abstract: High energy neutrino physics has been an active field of research at all proton accelerators over the last two decades and has played a key role in the development and verification of the standard model. The author reviews the experimental techniques of neutrino physics, traces the main developments, summarises the present status of the field and gives some hints on future activities. The author concentrates on those fields of physics where neutrino experiments have made unique contributions, namely the structure of the charged and neutral weak currents, the verification of the quark parton model and the determination of the quark and gluon distributions in the nucleon including their scaling violations, and the study of new particle production in neutrino interactions.
TL;DR: In this article, the authors review recent results from all these experiments and discuss the constraints they impose on neutrino masses and mixings, and discuss how neutrinoless double beta decay can be prevented.
Abstract: Finite neutrino masses and mixings will lead to several effects which have been searched for in various experiments. First, the kinematic in weak decays of nuclei and mesons will be modified. Also the decay of heavy neutrinos into lighter ones become possible. Second, oscillations of neutrinos of one type into neutrinos of another type will occur which may be observable even if the masses are very small. Experiments using terrestrial and non-terrestrial neutrino sources have been performed. Third, provided neutrinos have Majorana masses, lepton-number-violating processes like neutrinoless double beta decay will take place. It is attempted here to review recent results from all these experiments, and to discuss the constraints they impose on neutrino masses and mixings.
TL;DR: In this article, the authors treat the study of electronic relaxation phenomena using Mossbauer spectroscopy and discuss the application of ab initio theories for the general case, including a detailed analysis of the microscopic mechanisms responsible for relaxation.
Abstract: In this review the authors treat the study of electronic relaxation phenomena using Mossbauer spectroscopy. First, examples are discussed where it is possible to reproduce the spectral lineshape by use of a stochastic theory. The general case is then considered, including a full discussion on the application of ab initio theories. There then follows a detailed analysis of the microscopic mechanisms responsible for relaxation in insulators (e.g. spin-phonon and spin-spin interactions) and metals. Finally, the fast relation limit is considered.
TL;DR: In this article, the authors describe topologically non-trivial field configurations occurring in the Abelian Higgs model, CPN models, O(N) sigma models and in Yang-Mills gauge theories both with a Higgs sector (monopoles) and without one (instantons).
Abstract: The authors outline homotopy theory and its application to field theory. They describe topologically non-trivial field configurations occurring in the Abelian Higgs model, CPN models, O(N) sigma models and in Yang-Mills gauge theories both with a Higgs sector (monopoles) and without one (instantons). Parameter quantisation via topology is also discussed for the cases of QCD3 and the Wess-Zumino effective action.
TL;DR: In this article, the physics of infrared detection is presented with emphasis on the electrical properties of semiconductors involved in photoconductors, photovoltaic and thermal detectors, which are the main types of detectors used in arrays.
Abstract: The difficulty of infrared detection lies in the presence of an environmental background flux, from different sources, and of variable intensity. Its contribution to the measured signal must be discriminated from the flux of the source, using different cancellation techniques. The sensitivity of the measurement is often limited by the statistical fluctuations of the background emission, less frequently by those of the source emission, or by the system read-out noise. The physics of infrared detection is presented with emphasis on the electrical properties of semiconductors involved in photoconductors, photovoltaic and thermal detectors, which are the main types of detectors used in arrays. Three types of multiplexed output circuits have been developed: the charge injection devices (CID), the charge-coupled devices (CCD) and, more recently, the direct voltage readout (DVR). Their operation modes and peculiarities are analysed in light of their application to large infrared detector arrays. Infrared imaging is chiefly aimed at obtaining information on an object by a combination of spatial, spectral and temporal analyses of its light emission/reflection distribution. To this end, two-dimensional arrays introduce a huge multidetector gain over the earlier single-detector systems.
TL;DR: In this paper, the principal types of alpha particle interactions with nuclei up to an energy of 200 MeV are reviewed, together with the theories used to understand their mechanisms, and these enable a quantitative understanding of the reactions to be attained.
Abstract: The principal types of interactions of alpha particles with nuclei up to an energy of 200 MeV are reviewed, together with the theories used to understand their mechanisms. Elastic scattering is described by the optical model and this may be extended to include inelastic scattering by means of the coupled-channels formalism. The alpha particle may break up as it encounters the nuclear field and the fragments may or may not be captured by the nucleus. It is also possible for pick-up and stripping reactions to occur, as well as fragmentation. If the alpha particle, or one or more of its fragments, is captured by the nucleus it initiates a cascade of interactions leading to an equilibrated system that subsequently decays by statistical evaporation. During the course of this cascade pre-equilibrium particles can be emitted. Theories of these processes are described and these enable a quantitative understanding of the reactions to be attained.
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TL;DR: In this paper, the authors discuss the physics of the hadrons containing charmed, bottom and top quarks and the most recent experimental results from the e+e- storage rings in the 3-12 GeV range of centre-of-mass energy.
Abstract: The author discusses the physics of the hadrons containing charmed, bottom and top quarks. The emphasis is on the most recent experimental results from the e+e- storage rings in the 3-12 GeV range of centre-of-mass energy: SPEAR at SLAC, DORIS at DESY, and the Cornell Electron Storage Ring CESR.
CERN1
TL;DR: In this article, the authors discuss the structure and physical consequences of global and local supersymmetric (SUSY) gauge theories, and explain what supersymmetry is, and its physical properties.
Abstract: The author discusses in some detail the structure and physical consequences of global and local supersymmetric (SUSY) gauge theories. He presents motivations for SUSY theories, explains what supersymmetry is, and its physical properties. The observable consequences of SUSY as low energies and superhigh energies are discussed. The physical structure of simple (N=1) local SUSY ( identical to supergravity) is given, together with the physics of simple supergravity both at superhigh as well as at low energies. The possible experimental evidence for supersymmetry is analysed and the conclusions are presented. It is found that gravitational effects, as contained in supergravity theories, may play a rather fundamental role at all energy scales. This strong interrelation between gravity and particle physics is unprecedented.