نتایج جستجو برای: positron annihilation

تعداد نتایج: 38674  

Journal: :Journal of Physics: Conference Series 2016

2008
Xiao-Jun Bi

In this paper we calculate the Galactic positron flux from dark matter annihilation in the frame of supersymmetry, taking the enhancement of the flux by existence of dark matter substructures into account. The propagation of positrons in the Galactic magnetic field is solved in a realistic numerical model GALPROP. The secondary positron flux is recalculated in the GLAPROP model. The total posit...

2006
Xiao-Jun Bi

In this paper we calculate the Galactic positron flux from dark matter annihilation in the frame of supersymmetry, taking the enhancement of the flux by existence of dark matter substructures into account. The propagation of positrons in the Galactic magnetic field is solved in a realistic numerical model GALPROP. The secondary positron flux is recalculated in the GLAPROP model. The total posit...

2005
A. Baranowski M. Kostrzewa M. Szuszkiewicz

Weighted difference curves have been shortly presented as a proper tool allowing to analyze in another way two-detector Doppler spectra regarding positron annihilation with admixture electrons in some nickel alloys. The analysis of low and middle momentum parts of Doppler spectra for investigated alloys reflects the annihilation of positrons with admixture electrons. There is no distinct signal...

2005
L J M Dunlop G F Gribakin

A many-body theory approach to the calculation of gamma spectra of positron annihilation on many-electron atoms is developed. We evaluate the first-order correlation correction to the annihilation vertex and perform numerical calculations for the noble gas atoms. Extrapolation with respect to the maximal orbital momentum of the intermediate electron and positron states is used to achieve conver...

2005
J. Laverock S. B. Dugdale M. A. Alam H. H. Wills I. R. Fisher G. Santi

The Fermi surface of rare-earth tritellurides sRTe3d is investigated in terms of the nesting-driven chargedensity wave formation using positron annihilation and first-principles linear muffin-tin orbital calculations. Fermi surface nesting is revealed as a strong candidate for driving charge-density wave formation in these compounds. The nesting vector obtained from positron annihilation experi...

1999
T. C. Leung Z. A. Weinberg G. W. Rubloff

Variable-energy positron annihilation depth-profiling has been applied to the study of the Si/SiOz interface in Al-gate metal-oxide-semiconductor (MOS) structures. For both nand ptype silicon under conditions of negative gate bias, the positron annihilation S-factor characteristic of the interface (Sint) is substantially modified. Temperature and annealing behavior, combined with known MOS phys...

2007
S. W. H. Eijt A. J. Houtepen P. E. Mijnarends A. Bansil

A brief review is given of recent positron studies of metal and semiconductor nanocrystals. The prospects offered by positron annihilation as a sensitive method to access nanocrystal (NC) properties are described and compared with other experimental methods. The tunability of the electronic structure of nanocrystals underlies their great potential for application in many areas. Owing to their l...

2005
R. Yu T. Suzuki Y. Ito N. Djourelov K. Kondo

Coincidence Doppler broadening spectroscopy was applied to study n-hexane (C6H14), cyclohexane (C6H12) and cyclohexanone (C6H10O), at solid, as well as liquid states. The experiments were performed in parallel with traditional positron annihilation lifetime spectroscopy. Significant positron trapping by oxygen was observed in cyclohexanone; the oxygen effect is stronger in liquid state than in ...

Journal: :Physical review letters 2002
G F Gribakin J Ludlow

The behavior of the positron- 2 gamma annihilation rate on an atomic target near the positronium (Ps) formation threshold is determined. When the positron energy epsilon approaches the threshold epsilon(thr) from below, the effective number of electrons contributing to the annihilation, Z(eff), grows as Z(eff) approximately A/square root of [epsilon(thr)-epsilon], where A is related to the size...

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