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2 edition of Local and non-local aspects of positron annihilation in metals and alloys. found in the catalog.

Local and non-local aspects of positron annihilation in metals and alloys.

Dennis Gordon Lock

Local and non-local aspects of positron annihilation in metals and alloys.

by Dennis Gordon Lock

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Published by University of East Anglia in Norwich .
Written in English


Edition Notes

Thesis (Ph.D.) - University of East Anglia, School of Mathematics and Physics, 1974.

ID Numbers
Open LibraryOL13845516M

Positron Annihilation in Material Research • Introduction • Positron sources, positron beams • Interaction of positrons with matter • Annihilation channels: Emission of 1, 2 or 3 γ-quanta • Annihilation spectroscopies: Lifetime, angular correlations, Doppler broadening • Study of solid state properties by annihilation • Medical. action, and recovery in metals and alloys [7,8]. Due to the complexity of data interpretation most of the earlier positron annihilation studies on defects were limited to simple metals and alloys rather than complex nanocrys-talline materials. Recently, several researchers have used this technique to obtain a more detailed picture of the.

The positron annihilation, experimental and theoretical results obtained for bismuth are presented, mainly concerning the open volume defects created during compression and dry sliding. Positron lifetime in vacancy clusters increases with the size of the cluster; however, it saturates at the value of about ns already for six vacancies in a cluster. Similar values were resolved in the Author: Jerzy Dryzek. Positron annihilation studies of heavy-fermion metals and related compounds Maurizio Biasini December This thesis has been submitted to the Science Faculty at the University of Bristol in Candidature for the degree of Ph.D.

The School was primarily devoted to new concepts in the theory of magnetism in metals, alloys, and metallic compounds, but, as can be seen from the table of contents of the book, other topics of the theory of magnetism were also discussed in the course of the lec tures. The electron–positron annihilation process is the physical phenomenon relied on as the basis of positron emission tomography (PET) and positron annihilation spectroscopy (PAS). It is also used as a method of measuring the Fermi surface and band structure in metals by a technique called Angular Correlation of Electron Positron Annihilation Radiation. It is also used for nuclear transition.


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Local and non-local aspects of positron annihilation in metals and alloys by Dennis Gordon Lock Download PDF EPUB FB2

Including a short historical survey, the annihilation processes in metals and alloys are discussed and various physical conditions such as ordering processes, magnetic phenomena, liquid state, superconductivity and lattice imperfections are considered.

Finally, the present state of theoretical investigation is given and the outlook for Cited by: Local and non-local aspects of position annihilation in metals and alloys Author: Lock, D. ISNI: Awarding Body: University of East Anglia Current Institution: University of East Anglia Date of Award: Availability of Full Text.

On the Positron Annihilation in Metals. coupled with the development of a state-of-the-art non-local density functional theory approach. annealing behavior of aluminum alloys studied by. Some theoretical aspects, practical results and experimental techniques of use of the positron annihilation phenomena in the research of the structure, defects of structure and other properties of different materials and mediums are covered in this journal volume.

It comprises the papers presented at the 17th International Conference on Positron Annihilation (ICPA, Wuhan, China, Positron Annihilation 1 PRINCETON UNIVERSITY Physics Department Advanced Laboratory POSITRON ANNIHILATION IN A METAL Introduction Certain radioactive isotopes decay by emitting positrons, and the positrons can be used to probe the structure of solid materials.

For example, you can investigate the momentum distribution of conduction electrons in a metal. annihilation is responsible for the major part of the experimental tails. The result of Berko and Plaskett,that core annihilation~ responsible for the tails, coupled with Kahana's results for the valence electrons,give an adequate explaination of the main features of positron annihilation in many metals.

An adequate description of positron annihilation rates in metals is obtained by extension of the high-density limit, for annihilation in an electron gas, to realistic densities. A short-range electron-positron force is obtained in the high-density limit and is used to treat accurately the two-body correlations between the positron and metallic.

Jun 01,  · The computed lifetimes of positrons are longer than those calculated by Kahana. The effects of the long range Coulomb interaction on the annihilation rates are investigated. It is pointed out that the two-photon annihilation process accompanied by a plasmon emission in metals with low electron densities may not be runrevlive.com by: 5.

mainly through so called pick-off process: annihilation of the positron in the positronium with one surrounding electron in the material. There are three main techniques of positron annihilation spectroscopy and which can be used both with the positrons from sources and slow positron beams: 1) positron annihilation.

A high resolution positron annihilation angular distribution study has been made of a sequence of α-phase alloys, of copper gallium and copper germanium up to electron per atom ratios of about n = While the primary study has concerned the variation of the radius of the neck features of the Fermi surface with electron concentration, data has also been obtained for the Fermi cut-off.

For metals, however, the dimensions of the Fermi surface may be obtained by other methods such as the de Haas-van Alphen (dHvA) effect, the magnetoresistance effect, the rf size effect, etc., that are often capable of a greater precision than positron runrevlive.com by: • positron wave-function can be localized in the attractive potential of a defect.

• annihilation parameters change in the localized state. • e.g. positron lifetime increases in a vacancy. • lifetime is measured as time difference between appearance of (start) and MeV (stop) quanta. Positron Annihilation Studies of the Subsurface Zone Fig. The positron lifetime as a function of the depth measured for the specimens For both alloys, the well-deflned positron lifetime proflle of the subsurface region arose already for a sliding distance of a few meters.

For pure aluminium the positron lifetime after a clearly. Positron annihilation lifetime of the Mg-Zn-Y alloys. Table 1 shows the positron lifetime of the Mg-Zn-Y alloys measured at K. After subtracting the contribution from source component (τ. s = ps, I. s =%) and background, all the positron lifetime spectra of the Mg-Zn-Y alloys comprised only a single lifetime component (τ.

Jun 27,  · Positron lifetime studies on the chemically synthesized equiatomic FeCo magnetic nanoparticles with flower-like morphology are reported and compared with Fe, Co and FeCo annealed at various temperatures.

The FeCo is characterized by different lifetime components corresponding to positron annihilation events in vacancies Cited by: 3. Application of Positron Annihilation Spec troscopy to Studies of Subsurface Zones Induced by Wear in Magnesium and its Alloy AZ31 Fig. The positron paths in a metal crystal lattice.

Positron moves across interstitial regions between the ions or atoms (big grey spheres) and finally finds an electron (small grey spheres).

positron annihilation to share information on recent progress in this field. The main topics include a wide range of subjects involving fundamental aspects, applications as well as instrumentation.

Keynote speakers will introduce subjects of broad interest and stimulate discussions. The important many electron aspects of positron annihilation in metals are dealt with at runrevlive.com latter and larger part of this article is concerned with applications. Jul 01,  · Positron Annihilation: Experiment and Theory Stretched Chemical Bonds, Electron Correlation and Extended Defect Propagation Readership: Researchers and students in materials science, solid state physics and physical metallurgists.

The positron lifetime spectroscopy Martin-Luther-Universität Halle • positron wave-function can be localized in the attractive potential of a defect • annihilation parameters change in the localized state • e.g.

positron lifetime increases in a vacancy • lifetime is measured as time difference between appearance of (start). The positron annihilation (PA) method is sensitive for microstructural defects (see NDT Techniques: Positron Annihilation and Mössbauer Techniques).

If a positron beam is made to be incident in the presence of vacancy-type defects in metals, the defects are associated with enhanced positron lifetime depending on their nature and size, leading to the narrowing of the two-photon angular correlation or .Dec 02,  · Rapidly Quenched Metals, Volume I covers the proceedings of the Fifth International Conference on Rapidly Quenched Metals, held in Wurzburg, Germany on SeptemberThe book focuses on amorphous and crystalline metals formed by rapid quenching from the runrevlive.com Edition: 1.A Study of Defects in Iron Based Alloys by Positron Annihilation Techniques rounding electrons, conveying the information on the local electronic environment around the vacancy-type defects, therefore the defect structure after deformation A Study of Defects in Iron Based Alloys Fig.

2. The relation between the positron.