STFC has developed a novel ionising particle analyser which enables the separation of the fluorescent yield and electron yield in EXAFS (extended X-ray absorption fine structure) measurements. The technology greatly improves the study of surface layers of materials using X-ray light sources.
DESCRIPTION
Measurement of electron yield is a known technique which is used to study the response of material surfaces to interactions with beams of high energy photons such as X-rays. The total electron yield (TEY) of the emissive electrons includes both electrons emitted by the photoelectric effect and by the Auger effect. The energies of the Auger electrons emitted are characteristic of the atomic energy levels, providing a method of determining surface composition and character. However, instead of emitting an Auger electron, energy may be lost from the material as an X-ray. The fluorescent yield (FY) is the probability of a specific excited atom emitting a photon in preference to an Auger electron.
The new ionising analyser provides the ability to distinguish between TEY and FY by using a filter between the sample and detector. The filter will prevent charged particles emitted from the sample by X-ray irradiation as well as the secondary electrons emitted by such charged particles upon interacting with the ionisable gas. Thus only the uncharged particles which are photons emitted from the sample can pass the filter and excite the ionising gas to generate secondary electrons which is detected by the detector. Using this or other configurations of the filter and other aspects of the system, the required separation of TEY and FY can be done.
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