Doppler-broadening measurements of positron annihilation with high-momentum electrons in pure elements

Brusa, R. S.; Deng, Wen; Karwasz, Grzegorz P.; Zecca, Antonio

doi:10.1016/s0168-583x(02)00953-9

Cited by 102 publications

(61 citation statements)

References 28 publications

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“…In porous glasses, the o-Ps lives up to tens of ns [1]. Positron lifetimes are much shorter, 100-200 ps in metals [2] or semiconductors [3]. Tiny (few ps, imposed on 220 ps) differences of positron lifetimes in Czochralski-grown silicon allowed to detect clustering of oxygen atoms around defects [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…A new generation of positron lifetime spectrometers, with resolution down to 160-180 ps [9] allowed to find matching between experiments in high-purity, monocrystal metals and theories [2]. Decomposition of lifetimes into very short (100-200 ps) and longer components (150-300 ps) allowed in metal to determine the kind and concentration of point-like defects; similarly in semiconductors [10].…”

Section: Introductionmentioning

confidence: 99%

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Positronium Formation in Organic Liquids

et al. 2017

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This paper reports on the results of positron annihilation lifetime measurements of three organic liquids: benzene (C6H6), cyclohexane (C6H12), and methanol (CH3OH). The lifetime spectra are acquired at different temperatures for non-degassed, degassed, and oxygen-saturated samples, at temperatures between 5 • C and 25 • C. The spectra are analyzed using a standard three-exponential model. The influence of oxygen on each lifetime and intensity component is discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Positronium Formation in Organic Liquids

et al. 2017

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“…The DB S curve has been deconvoluted using additional information from measurements by a coincidence method, in which the ambient gamma background at E   511 keV is reduced. This method allows to extract better signal from high-momentum (i.e., core) electrons, and in this way, detect the chemical species around defects, see [8]. Such curves are shown in Fig.…”

Section: Case Study II -Hydrogen and Helium In Siliconmentioning

confidence: 99%

“…The experiment is not easy, again. In pure metals, positron lifetimes are in the 100-200 ps range, see, for example, [8]. The fastest techniques show intrinsic resolutions not better than 160-180 ps, see, for example, [9].…”

Section: Toward a European Network Of Positron Laboratoriesmentioning

confidence: 99%

Toward a European Network of Positron Laboratories

et al. 2015

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Positron defectoscopyPositron annihilation is one of the few really nondestructive techniques in material science, giving unique information on types and concentrations of defects, even at a single parts per million (ppm) level, see, for example, [1]. Applications of positron annihilation techniques span from semiconductors [2,3] and metals [4] to polymers [5] and porous media [6]. In each case, answers given by positron methods are unique and complementary to other techniques.Two most common techniques, the analysis of Doppler broadening (DB) of the 511-keV annihilation line and the positron lifetime measurements, are to some extent complementary. The broadening brings information on momenta of electrons that positrons annihilate with. The main contribution to the annihilation comes from valence electrons, that is, possessing a few electron-volts energy. In the relativistic transformation, these energies translate to broadening of a few kiloelectron-volts, i.e. similar to the intrinsic resolution of gamma detectors used in experiments. Therefore, the information on relative contributions from valence and core (i.e., from defect sites) electrons is not straightforward. Somewhat phenomenological line-broadening parameters (central area S parameter, W lateral area, V 3 annihilation) are used, and some normalization is needed to make comparison between different experiments and theories. Evaluation of DB requires not only information of the overlap between a positron and electrons in the material but also a detailed

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“…So, a detailed knowledge of the configuration and energy of vacancies is very important for understanding many phenomena associated with vacancies. Many indirect experimental methods, such as by measurements of heat capacity (special heat) [4], electrical resistivity [5], differential-dilatometer (thermal expansion not caused by the lattice but by increased number of vacancies) [6] and positron annihilation spectrum [7], have been used to measure the vacancy formation energy. A theoretical calculation or simulation is a useful supplement method.…”

Section: Introductionmentioning

confidence: 99%

Atomic simulation of the vacancies in BCC metals with MAEAM

Zhang¹,

Wen²,

Xu³

2006

Open Physics

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The formation energy of the mono-vacancy and both the formation energy and binding energy of the di-and tri-vacancy in BCC alkali metals and transition metals have been calculated by using the modified analytical embedded-atom method (MAEAM). The formation energy of each type of configuration of the vacancies in the alkali metals is much lower than that in the transition metals. From minimum of the formation energy or maximum of the binding energy, the favorable configuration of the di-vacancy and tri-vacancy respectively is the first-nearest-neighbor (FN) or second-nearest-neighbor (SN) di-vacancy and the [112] tri-vacancy constructed by two first-and one second-nearest-neighbor vacancies. It is indicated that there is a concentration tendency for vacancies in BCC metals.

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Doppler-broadening measurements of positron annihilation with high-momentum electrons in pure elements

Cited by 102 publications

References 28 publications

Positronium Formation in Organic Liquids

Positronium Formation in Organic Liquids

Toward a European Network of Positron Laboratories

Atomic simulation of the vacancies in BCC metals with MAEAM

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