Gamma Spectra Resulting from the Annihilation of Positrons with Electrons in a Single Core Level

Eshed, Anat; Goktepeli, S.; Köymen, A. R.; Kim, S.; Chen, W. C.; O’Kelly, D.; Sterne, P. A.; Weiss, A. H.

doi:10.1103/physrevlett.89.075503

Cited by 20 publications

(17 citation statements)

References 15 publications

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“…Positron annihilation on core electrons is also a key process in the surface-analytic positroninduced Auger-electron spectroscopy (PAES) [7][8][9][10], and the time-resolved PAES [11], which enables the study of dynamics of catalysis, corrosion, and surface alloying [12]. Coincident measurements of the annihilation γ-ray and Auger electrons allows one to determine the annihilation γ-ray spectra for individual core orbitals [13,14].…”

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confidence: 99%

γ-Ray Spectra and Enhancement Factors for Positron Annihilation with Core Electrons

Green

Gribakin

2015

Phys. Rev. Lett.

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Many-body theory is developed to calculate the γ-spectra for positron annihilation with valence and core electrons in the noble gas atoms. A proper inclusion of correlation effects and core annihilation provides for an accurate description of the measured spectra [Iwata et al., Phys. Rev. Lett. 79, 39 (1997)]. The theory enables us to calculate the enhancement factors γ nl , which describe the effect of electron-positron correlations for annihilation on individual electron orbitals nl. We find that the enhancement factors scale with the orbital ionization energy I nl (in electron-volt), as γ nl = 1 + A/I nl + (B/I nl ) β , where A ≈ 40 eV, B ≈ 24 eV and β ≈ 2.3.

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confidence: 99%

γ-Ray Spectra and Enhancement Factors for Positron Annihilation with Core Electrons

Green

Gribakin

2015

Phys. Rev. Lett.

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“…The total core density is a sum of contributions from occupied shells. In practice, discrepancies between measured and calculated spectra have been found for Cu 3p and Ag 4p core states [1]. This fact was attributed by the authors to likely mixed s-p positron state at the surface and approximation used for γ(r) in Eq.…”

Section: Introductionmentioning

confidence: 84%

“…Recent experiments demonstrate that the application of positron annihilation induced Auger electron spectroscopy combined with Doppler broadening technique makes it possible to map the electron-positron (e-p) momentum densities for electrons from individual core shells [1]. The Doppler spectra from core electrons may be interpreted as one-dimensional (1D) projections of the relevant e-p momentum densities, i.e.…”

Section: Introductionmentioning

confidence: 99%

Electron-Positron Momentum Densities for Electrons from Individual Core Levels

Rubaszek

2005

Acta Phys. Pol. A

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“…Here we want to draw attention to the positron annihilation on the inner electron shells [13][14][15][16] as a potential test of the expression (16). In the non-relativistic approximation the annihilation vertex is proportional to the δfunction.…”

Section: Positron Annihilation On Inner Electronsmentioning

confidence: 99%

“…Consequently the accurate study of the annihilation line shape provides information about the inner shell contribution [13]. The inner shell annihilation was also detected directly with the coincidence technique for γ quanta and Auger electrons [14].…”

Section: Positron Annihilation On Inner Electronsmentioning

confidence: 99%

Exchange-assisted tunneling and positron annihilation on inner atomic shells

Kozlov

Flambaum

2013

Phys. Rev. A

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It is known for a long time that the long range asymptotic behavior of the Hartree-Fock orbitals is different from that of the orbitals in the local potential. However, there is no consensus about observable physical effects associated with this asymptotics. Here we argue that weaker decrease of the Hartree-Fock orbitals at large distances is responsible for the positron annihilation on the inner shell electrons, which is observed experimentally.PACS numbers: 31.15.A-, 03.65.Ge Long distance behaviour of electron orbitalsIt is sometimes assumed that exchange interaction between electrons is important only at short distances and can be neglected when one of the electrons is far from the origin. It is easy to see that this is not true if we consider long range asymptotics of an inner shell electron [1][2][3]. At large distances the exchange term for all occupied orbitals has the form r −ν φ v , where φ v is the outermost orbital with the highest energy ε v . The power ν depends on the leading multipolarity of the exchange interaction. The monopole component does not contribute to the asymptotics due to the orthogonality of the orbitals and for the dipole component of the exchange interaction ν = 2.This fact was first realized by Handy et al.[1], who showed that generally speaking asymptotic behavior of all Hartree-Fock orbitals is given by the exponential with the highest energy ε v (or the smallest binding energy):where ν i is specific for each orbital and r v is the radius of the outermost atomic orbital. We use atomic units h = m e = |e| = 1 unless stated otherwise. Because the monopole component of the exchange interaction does not contribute to the asymptotic behaviour, the expression (1) does not apply to the systems where only sorbitals are occupied.Later the asymptotic behaviour of the electron orbitals was reanalyzed by many authors [2][3][4][5][6]. Dzuba et al. [2] showed that the asymptote (1) holds for the relativistic Hatree-Fock-Dirac equations as well. The role of correlations were studied by Morrell et al. [4] and Katriel and Davidson [5], who demonstrated that Eq. (1) holds also for the natural orbitals φ nat i with nonzero occupation numbers. Natural orbitals are the eigenfunctions of the one electron density matrix ρ(x , x), where x ≡ r, σ and they can be found for any many electron wavefunction.Natural orbitals are mostly used in the context of the configuration interaction approach. For the corevalence correlations the many-body perturbation theory (MBPT) is usually more efficient. Within MBPT approach Flambaum [3] showed that Eq. (1) also holds for the Brueckber orbitals. The latter are solutions of the one particle equation with the correlation potential Σ added to the Hartree-Fock potential. The nonlocal part of the potential Σ decreases faster than the exchange potential and therefore does not change the long range behaviour of the Brueckner orbitals.In the solid state physics the long range exchange induced interaction is well known.For example, the Ruderman-Kittel-Kasuya-Yasida (RKKY) exc...

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Gamma Spectra Resulting from the Annihilation of Positrons with Electrons in a Single Core Level

Cited by 20 publications

References 15 publications

γ-Ray Spectra and Enhancement Factors for Positron Annihilation with Core Electrons

γ-Ray Spectra and Enhancement Factors for Positron Annihilation with Core Electrons

Electron-Positron Momentum Densities for Electrons from Individual Core Levels

Exchange-assisted tunneling and positron annihilation on inner atomic shells

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