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Characterisation of the Physical, Chemical and Electronic Properties of Solids on the Nanometre Scale

Surface Physics with Positrons
The study of slow positron interactions with surfaces continues to provide new insights into the fundamental interactions of charged particles with matter, and has also led to unique methods for testing quantum electrodynamics, to fundamental atomic physics experiments, and to the pioneering application of positron-surface phenomena to the study of the chemical and physical properties of solid surfaces. Slow positrons incident on solid surfaces may be re-emitted into the vacuum via backscattering, diffraction, or thermalisation followed by ejection by a negative work function. Additionally, positrons may eject electrons from a surface as secondary electrons (following impact ionisation) or Auger electrons (following annihilation of surface core electrons).  

The re-emitted positron spectrometer

The re-emitted positron spectrometer

The re-emitted positron spectrometer

The re-emitted positron spectrometer

Work performed by the Bath slow positron group has included (a) re-emitted positron energy spectroscopy; the energy spectra of re-emitted positrons are highly sensitive to the physical and chemical state of the surface: (b) secondary electron emission by positron impact, which allows the use of low incident energies inaccessible to electrons (for which there is unavoidable confusion between re-emitted primary electrons and true secondaries): and (c) positron re-emission microscopy, discussed elsewhere on this site.

Professor P. G. Coleman, University of Bath

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