Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/234129

Download PDF (Published version) (Adobe Acrobat PDF, -1 bytes)

Title

Effects of quantum chemistry models for bound electrons on positron annihilation spectra for atoms and small molecules

Author(s)

Wang, Feng;  Ma, Xiaoguang;  Selvam, Lalitha;  Gribakin, Gleb;  Surko, Clifford M.

Abstract

The Doppler-shift spectra of the -rays from positron annihilation in molecules were determined by using the momentum distribution of the annihilation electron-positron pair. The effect of the positron wavefunction on spectra was analysed in a recent paper (Green et al 2012 New J. Phys. 14 035021). In this companion paper, we focus on the dominant contribution to the spectra, which arises from the momenta of the bound electrons. In particular, we use computational quantum chemistry models (Hartree-Fock with two basis sets and density functional theory (DFT)) to calculate the wavefunctions of the bound electrons. Numerical results are presented for noble gases and small molecules such as H 2, N 2, O 2, CH 4 and CF 4. The calculations reveal relatively small effects on the Doppler-shift spectra from the level of inclusion of electron correlation energy in the models. For atoms, the difference in the full-width at half-maximum of the spectra obtained using the Hartree-Fock and DFT models does not exceed 2%. For molecules the difference can be much larger, reaching 8% for some molecular orbitals. These results indicate that the predicted positron annihilation spectra for molecules are generally more sensitive to inclusion of electron correlation energies in the quantum chemistry model than the spectra for atoms are.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Life and Social Sciences

Source

New Journal of Physics, Vol. 14 (Aug 2012), article no. 085022

Publication year

2012

FOR Code(s)

02 Physical Sciences

Keyword(s)

Density-functional theory;  Electron and positron scattering;  Electron correlation calculations for diatomic molecules;  Self-consistent-field methods

Publisher

Institute of Physics Publishing

ISSN

1367-2630

Publisher URL

http://dx.doi.org/10.1088/1367-2630/14/8/085022

Copyright

Copyright © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. The published version is reproduced in accordance with the terms of the Creative Commons Attribution-Non-Commercial-ShareAlike 3.0 licence (http://creativecommons.org/licenses/by-nc-sa/3.0/).

Additional information

Supported by the Australian Research Council.

Full text

Peer reviewed