Bulk and surface evidence for the long-range spatial modulation of X-ray absorption in the Al-Pd-Mn quasicrystal at Bragg incidence

An X-ray standing waves experiment was performed at the ID32 beam line of the ESRF on an Al-Pd-Mn quasicrystal with the X-ray beam at normal incidence. The X-ray photoemission core levels for each element were recorded to probe the surface. The drain current, i.e. the electron current from ground needed to neutralize the irradiated sample and to compensate the photoemitted electrons was also recorded as a bulk probe that integrates over all atoms of the sample. Within the two-beam approximation applied to quasicrystals, a simple analysis of this effect is proposed. This provides a direct-space illustration of the diffraction process in a quasiperiodic structure.