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  Electron and positron pair emission by low energy positron impact on surfaces

Schumann, F. O., Brandt, I., Wei, Z., Kirschner, J., Giebels, F., Gollisch, H., et al. (2021). Electron and positron pair emission by low energy positron impact on surfaces. Progress in Surface Science, 96(2): 100629. doi:10.1016/j.progsurf.2021.100629.

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https://doi.org/10.1016/j.progsurf.2021.100629 (Publisher version)
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Schumann, F. O.1, Author              
Brandt, I.S.2, Author
Wei, Z.2, Author
Kirschner, J.2, Author
Giebels, F.3, Author
Gollisch, H.3, Author
Feder, R.3, Author
Affiliations:
1Department of Synthetic Materials and Functional Devices (SMFD), Max Planck Institute of Microstructure Physics, Max Planck Society, ou_3316580              
2Max Planck Institute of Microstructure Physics, Max Planck Society, Weinberg 2, 06120 Halle, DE, ou_2415691              
3External Organizations, ou_persistent22              

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 Abstract: The emission of electron pairs from surfaces has the power to reveal details about the electron–electron interaction in condensed matter. This process, stimulated by a primary electron or photon beam, has been studied both in experiment and theory over the last two decades. An additional pathway, namely positron–electron pair emission, holds the promise to provide additional information. It is based on the notion that the Pauli exclusion principle does not need to be considered for this process. We have commissioned a laboratory based positron source and performed a systematic study on a variety of solid surfaces. In a symmetric emission geometry we can explore the fact that positron and electron are distinguishable particles. Following fundamental symmetry arguments we have to expect that the available energy is shared unequally among positron and electron. Experimentally we observe such a behavior for all materials studied. We find an universal feature for all materials in the sense that on average the positron carries a larger fraction of the available energy. This is qualitatively accounted for by a simplified scattering model. Numerical results, which we obtained by a microscopic theory of positron–electron emission from surfaces, reveal however that there are also cases in which the electron carries more energy. Whether the positron or the electron is more energetic depends on details of the bound electron state and of the emission geometry. The coincidence intensity is strongly material dependent and there exists an almost monotonic relation between the singles and coincidence intensity. These results resemble the findings obtained in electron and photon stimulated electron pair emission. An additional reaction channel is the emission of an electron pair upon positron impact. We will discuss the energy distributions and the material dependence of the coincidence signal which shows similar features as those for positron–electron pairs.

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 Dates: 2021-05-282021-05
 Publication Status: Published in print
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 Identifiers: DOI: 10.1016/j.progsurf.2021.100629
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Title: Progress in Surface Science
  Abbreviation : Progr. Surf. Sci.
Source Genre: Journal
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Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 96 (2) Sequence Number: 100629 Start / End Page: - Identifier: ISSN: 0079-6816
CoNE: https://pure.mpg.de/cone/journals/resource/954925460091