Positron localization effects on the Doppler broadening of the annihilation line: Aluminum as a case study

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Journal Title
Journal ISSN
Volume Title
School of Science | A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2005
Major/Subject
Mcode
Degree programme
Language
en
Pages
054112/1-6
Series
Physical Review B, Volume 72, Issue 5
Abstract
The coincidence Doppler broadening (CDB) technique is widely used to measure one-dimensional momentum distributions of annihilation photons, with the aim of obtaining information on the chemical environment of open-volume defects. However, the quantitative analysis of CDB spectra needs to include also purely geometrical effects. A demonstration is given here, on the basis of CDB spectra measured in quenched and in deformed pure aluminum. The comparison of the experimental results with ab initio computations shows that the observed differences come from the difference in free volume seen by positrons trapped in quenched-in vacancies or in vacancylike defects associated to dislocations. The computation reproduces accurately all details of CDB spectra, including the peak near the Fermi break, which is due to the zero-point motion of the confined positron.
Description
Keywords
positron annihilation, coincidence Doppler broadening technique
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Citation
Calloni, A. & Dupasquier, A. & Ferragut, R. & Folegati, P. & Iglesias, M. M. & Makkonen, I. & Puska, Martti J. 2005. Positron localization effects on the Doppler broadening of the annihilation line: Aluminum as a case study. Physical Review B. Volume 72, Issue 5. 054112/1-6. ISSN 1550-235X (electronic). DOI: 10.1103/physrevb.72.054112.