Photoelectron emission: images and spectra

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Abstract
SUMMARY: We give an account of the development of electron emission imaging and the photoelectron emission process. We then describe a particular combination of photoelectron emission microscopy and photoelectron spectroscopy which we call photoelectron spectromicroscopy. This is achieved using a very strong, divergent magnetic field to define electron trajectories without the use of electron optical focusing. It is thus possible to produce electron images of the surfaces of three‐dimensional objects using low energy photoelectrons in which the image contrast is dependent upon, among other things, the yield and energy distribution functions. The various image contrast mechanisms which apply are outlined with illustrative examples. Techniques for energy analysis of the photoelectron image are described and examples of the photoelectron spectra of different regions of the surface of an object presented. Electron images produced by metastable atoms and slow ions are also discussed. The use of the magnetic field introduces the opportunity for a number of novel techniques which will be described.