ABSTRACT
In 1986, Abraham Szoke [1] proposed the concept of X-ray fluorescence holography (XFH). In this idea, a fluorescence hologram is formed by the interference between the direct waves from the photoexcited atoms and the waves scattered by the neighbouring atoms. It is called "inside source holography". According to the optical reciprocity theorem, the optical beam paths can be reversed and the positions of the source and the detector can then be exchanged. It is regarded as the inverse of XFH and called "inside detector holography". It is worthy of noting that different names are used for the same methods in some literatures concerning with atomic resolution holography. For short, one calls the inside source and the inside detector holography 'normal' and 'inverse' holography, respectively. Sometimes one refers to 'inverse' holography as 'multiple energy X-ray holography' (MEXH). 2. Principle of inside source holography An atom excited by external radiation emits X-ray fluorescence radiation propagating in the form of a spherical wave. The undisturbed wave reaching the detector directly serves as a reference wave, while the portion of the radiation elastically scattered by the neighbouring atoms constitutes the object wave. The hologram is formed by the interference between the reference and the object waves, as shown in figurei.
