Electron shell contributions to gamma-ray spectra of positron annihilation in noble gases

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Title: Electron shell contributions to gamma-ray spectra of positron annihilation in noble gases
Author(s): Wang, Feng; Selvam, Lalitha; Gribakin, Gleb F.; Surko, Clifford M.
Abstract: Gamma-ray positron annihilation spectra of the noble gases are simulated using computational chemistry tools for the bound electron wavefunctions and plane-wave approximation for the low-energy positron. The present annihilation line shapes, i.e. the full width at half maximum, Delta epsilon, of the gamma-ray annihilation spectra for He and Ar (valence) agree well with available independent atomic calculations using a different algorithm. For other noble gases they achieve moderate agreement with the experimental measurements. It is found that the contributions of various atomic electron shells to the spectra depend significantly on their principal quantum number n and orbital angular momentum quantum number l. The present study further reveals that the outermost ns electrons of the noble gases exhibit spectral line shapes in close agreement with those measured, indicating (as expected) that the measurements are not due to a simple sum over the momentum densities for all atomic electrons. The robust nature of the present approach makes it possible for us to proceed to more complex molecular systems using the tools of modern computational chemistry.
Publication type: Journal article
Research centre: Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Molecular Simulation
Source: Journal of Physics B: Atomic, Molecular and Optical Physics, Vol. 43, no. 16 (Aug 2010), article no. 165207
Publication year: 2010
FOR Code(s): 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0205 Optical Physics
Keyword(s): Atoms; Molecules; Momentum spectroscopy; Wave-funtions
Publisher: Institute of Physics Publishing
ISSN: 0953-4075
Publisher URL: http://dx.doi.org/10.1088/0953-4075/43/16/165207
Additional information: The research from which this paper is derived featured in the November 2010 issue of the Swinburne Magazine. For more information, see: http://www.swinburne.edu.au/magazine/11/193/life---s-recipe-book-calls-for-a-pinch-of-antimatter/
Peer reviewed