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Dynamic scattering of electron vortex beams – A Bloch wave analysis

Mendis, B.G.

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Abstract

Two important applications of electron vortex beams are in electron magnetic chiral dichroism (EMCD) measurements and nanoparticle manipulation. In both cases orbital angular momentum (〈Lz〉) transfer between the vortex beam and the specimen due to dynamic scattering is critical. In general the 〈Lz〉 pendellösung consists of short and long wavelength oscillations. The former is due to interference between the tightly bound 1s and more dispersive non-1s Bloch states, while the latter is due to interference between the non-1s states. For EMCD experiments with ±ħ angular momentum beams, momentum transfer can be minimised by selecting the appropriate aperture size, so that the probe wavefunction approximately matches that of the 2p-type Bloch states. For manipulating nanoparticles with large angular momentum beams small apertures are required to excite the 1s state and thereby enhance the short wavelength oscillations in 〈Lz〉. This enables efficient momentum transfer to the specimen, provided the nanoparticle dimension corresponds to a minimum in the 〈Lz〉 pendellösung.

Citation

Mendis, B. (2015). Dynamic scattering of electron vortex beams – A Bloch wave analysis. Ultramicroscopy, 149, 74-85. https://doi.org/10.1016/j.ultramic.2014.11.001

Journal Article Type Article
Acceptance Date Nov 6, 2014
Online Publication Date Nov 10, 2014
Publication Date Feb 1, 2015
Deposit Date Dec 10, 2014
Publicly Available Date Dec 11, 2014
Journal Ultramicroscopy
Print ISSN 0304-3991
Electronic ISSN 1879-2723
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 149
Pages 74-85
DOI https://doi.org/10.1016/j.ultramic.2014.11.001
Keywords Electron vortex beams, Angular momentum, Electron magnetic chiral dichroism (EMCD), Nanoparticle manipulation.
Public URL https://durham-repository.worktribe.com/output/1440211

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Copyright Statement
NOTICE: this is the author’s version of a work that was accepted for publication in Ultramicroscopy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ultramicroscopy, 149, February 2015, 10.1016/j.ultramic.2014.11.001.






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