A surprise in the first Born approximation for electron scattering

Michael Treacy, D. Van Dyck

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

A standard textbook derivation for the scattering of electrons by a weak potential under the first Born approximation suggests that the far-field scattered wave should be in phase with the incident wave. However, it is well known that waves scattered from a weak phase object should be phase-shifted by π/2 relative to the incident wave. A disturbing consequence of this missing phase is that, according to the Optical Theorem, the total scattering cross section would be zero in the first Born approximation. We resolve this mystery pedagogically by showing that the first Born approximation fails to conserve electrons even to first order. Modifying the derivation to conserve electrons introduces the correct phase without changing the scattering amplitude. We also show that the far-field expansion for the scattered waves used in many texts is inappropriate for computing an exit wave from a sample, and that the near-field expansion also give the appropriately phase-shifted result.

Original languageEnglish (US)
Pages (from-to)57-62
Number of pages6
JournalUltramicroscopy
Volume119
DOIs
StatePublished - Aug 2012

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Born approximation
Electron scattering
electron scattering
Scattering
far fields
Electrons
derivation
textbooks
electrons
expansion
Textbooks
scattering amplitude
scattering cross sections
near fields
theorems
scattering

Keywords

  • First Born approximation
  • Weak phase object

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Instrumentation
  • Electronic, Optical and Magnetic Materials

Cite this

A surprise in the first Born approximation for electron scattering. / Treacy, Michael; Van Dyck, D.

In: Ultramicroscopy, Vol. 119, 08.2012, p. 57-62.

Research output: Contribution to journalArticle

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