Two-dimensional Momentum Distribution Measurements in Metals and Disordered Alloys by Positron Annihilation PDF Download
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Author: John Jan Mader
Publisher:
ISBN:
Category : Fermi surfaces
Languages : en
Pages : 216
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Book Description
Author: John Jan Mader
Publisher:
ISBN:
Category : Fermi surfaces
Languages : en
Pages : 216
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Book Description
Author:
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 1008
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Theoretical and experimental progess in connection with 2D-ACAR positron annihilation studies of ordered, disordered, and defected alloys is discussed. We present, in particular, some of the recent developments concerning the electronic structure of disordered alloys, and the work in the area of annihilation from positrons trapped at vacancy-type defects in metals and alloys. The electronic structure and properties of a number of compounds are also discussed briefly; we comment specifically on high T/sub c/ ceramic superconductors, Heusler alloys, and transition-metal aluminides. 58 refs., 116 figs.
Author: George S. Komada
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 66
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Author:
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Category :
Languages : en
Pages :
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Book Description
The current renaissance of investigations of positron annihilation in solids has its origins in the observation that positrons interact strongly with certain crystal-lattice defects. Three properties of the annihilation process are being measured to gain information about the defects or about the local environment of the positron at the instant of its annihilation: positron lifetime, angular correlation of the two annihilation quanta, and Doppler broadening of the 511-keV annihilation line. Until the physics of positron behavior in solids is fully understood, the phenomenon will continue to be useful in a manner analogous to electrical resistivity recovery for identifying the recovery stages in irradiated metals. Ultimately, it is destined to provide detailed quantitative information such as the formation volume of vacancies, vacancy-impurity binding energies and electron momentum distributions and densities at defect sites. 2 tables, 52 refs. (auth).
Author:
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Category :
Languages : en
Pages :
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Positron annihilation, especially the angular correlation of annihilation radiation, is a powerful tool for investigating the electronic spectra of ordered as well as defected materials. The tendency of positrons to trap at vacancy-type defects should enable this technique to study the local environment of such defects. However, we need to develop a theoretical basis for calculating the two-photon annihilation momentum density rho/sub 2gamma/(p-vector). We have recently formulated and implemented a theory of rho/sub 2gamma/(p-vector) from vacancy-type defects in metals and alloys. This article gives an outline of our approach together with a few of our results. Section 2 summarizes the basic equations for evaluating rho/sub 2gamma/(p-vector). Our Green's function-based approach is nonperturbative and employs a realistic (one-particle) muffin-tin Hamiltonian for treating electrons and positrons. Section 3 presents and discusses rho/sub 2gamma/(p-vector) results for a mono-vacancy in Cu. We have neglected the effects of electron-positron correlations and of lattice distortion around the vacancy. Section 4 comments briefly on the question of treating defects such as divacancies and metal-impurity complexes in metals and alloys. Finally, in Section 5, we remark on the form of rho/sub 2gamma/(p-vector) for a mono-vacancy in jellium. 2 figs.
Author: Allen P. Mills
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 360
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Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 964
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Alfredo Dupasquier
Publisher: IOS Press
ISBN: 9789051992038
Category : Electronic structure
Languages : en
Pages : 830
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Book Description
The lifetime of a positron inside a solid is normally less than a fraction of nanosecond. This is a very short time on a human scale, but is long enough to enable the positron to visit an extended region of the material, and to sense the atomic and electronic structure of the environment. Thus, we can inject a positron in a sample to draw from it some signal giving us information on the microscopic properties of the material. This idea has been successfully developed in a number of positron-based techniques of physical analysis, with resolution in energy, momentum, or position. The complex of these techniques is what we call now positron spectroscopy of solids. The field of application of the positron spectroscopy extends from advanced problems of solid-state physics to industrial applications in the area of characterization of high-tech materials. This volume focuses the attention on the physics that can be learned from positron-based methods, but also frames those methods in a wider context including other experimental approaches. It can be considered as a textbook on positron spectroscopy of solids, the sort of book that the newcomer takes for his approach to this field, but also as a useful research tool for the expert.
Author: P. Hautojärvi
Publisher: Springer Science & Business Media
ISBN: 364281316X
Category : Science
Languages : en
Pages : 266
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Book Description
In condensed matter initially fast positrons annihilate after having reached equi librium with the surroundings. The interaction of positrons with matter is governed by the laws of ordinary quantum mechanics. Field theory and antiparticle properties enter only in the annihilation process leading to the emergence of energetic photons. The monitoring of annihilation radiation by nuclear spectroscopic methods provides valuable information on the electron-positron system which can directly be related to the electronic structure of the medium. Since the positron is a positive electron its behavior in matter is especially interesting to solid-state and atomic physi cists. The small mass quarantees that the positron is really a quantum mechanical particle and completely different from any other particles and atoms. Positron physics started about 25 years ago but discoveries of new features in its interac tion with matter have maintained continuous interest and increasing activity in the field. Nowadays it is becoming part of the "stock-in-trade" of experimental physics.
