The Specific Primary Ionization and Energy Loss of Fast Electrons in Matter

In recent years, more notice has been given to the fact that the energy loss spectra of fast electrons transmitted through thin specimens may be employed to analyze their composition (e.g. refs. 1,2). A program to explore the usefulness of energy loss spectra (with a STEM) in identifying the components of biological membranes has been initiated.One would like to scan, for example, over an intact membrane surface and analyze, point by point, the composition. However, some preliminary studies are necessary: First, the energy loss spectra of each major membrane component must be determined; second, the change in these spectra with beam dose must be found, since damage may be a problem as resolution (and therefore dose) is increased; third, a practical scheme of obtaining point-bypoint data (i.e., pictures that relate composition to contrast) must be devised.

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Theoretical modelling of the size and shape of atomic images formed with inelastically scattered electrons

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137768 ◽

1995 ◽

Vol 53 ◽

pp. 278-279

Author(s):

O.F. Holbrook ◽

D.M. Bird

Keyword(s):

Energy Loss ◽

Inelastic Scattering ◽

Signal To Noise Ratio ◽

Single Atom ◽

Theoretical Modelling ◽

Resolution Limit ◽

Fast Electrons ◽

Size And Shape ◽

Characteristic Image ◽

Specific Amount

In electron diffraction the study of inelastic scattering processes has been revolutionised with the development of imaging PEELS. It is now relatively straightforward to produce images from fast electrons which have lost a specific amount of energy (to within about 5eV). Therefore electrons which have been inelastically scattered via an atomic transition, loosing a characteristic amount of energy, can in principle be used to form an equally characteristic image. It should be noted that such images will not be perfect since other single and multiple inelastic events may result in a similar energy loss which will tend to obscure the ideal picture. An important issue is the ultimate resolution limit of this type of atomic imaging. Although practical questions (such as signal-to-noise ratio) are important it is still interesting to ask what theoretical limit might be imposed by the underlying physics of the inelastic scattering and imaging processes. The work presented here is an initial investigation of the typical radial size and shape which can be expected when imaging a single atom and how these depend upon the transition and energy loss being considered.

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The energy loss by radiation of fast electrons in a Coulomb field

Mathematical Proceedings of the Cambridge Philosophical Society ◽

10.1017/s0305004100017771 ◽

1943 ◽

Vol 39 (2) ◽

pp. 127-130

Author(s):

J. C. Jaeger

Keyword(s):

Exact Solution ◽

Energy Loss ◽

Cross Sections ◽

Born Approximation ◽

Coulomb Field ◽

Wave Functions ◽

Fast Electrons ◽

Low Energies ◽

Relativistic Coulomb ◽

Relativistic Equations

The problem of the energy loss by radiation of an electron in a Coulomb field has been solved, using relativistic equations and the Born approximation, by Bethe and Heitler, and, using exact non-relativistic equations, by Sommerfeld; the first of these solutions is valid only for relatively high and the second for relatively low energies. In this paper an exact solution of the problem is given using the relativistic Coulomb wave functions, but depending on a final stage of numerical computation. The method is an extension of that used to determine cross-sections for pair production.

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