Theory of extended energy loss fine structure in the reflection mode

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Abstract
An analytic expression for the current detected in an extended energy loss fine structure experiment in the reflection mode is derived, which takes into account the diffraction by the atoms of the crystal of the two electrons participating in the excitation process. Within a single-scattering approximation, the authors show that the signal contains two oscillating factors, one of the EXAFS type and the other, which has been neglected in all studies until now, similar to a photo-electron diffraction signal. They perform a model computation in order to show the experimental conditions in which an EXAFS-type analysis still applies and the precision in the distances that may be expected. They also propose a new type of experiment in which the detection is angularly resolved and which would allow a bond angle determination in addition to the distance determination, under specified excitation conditions.