Resonant forbidden reflections in a Al-Cu-Rh(Al58Cu38Rh4) quasicrystal

The forbidden reflection is caused by the crystal symmetry in the diffraction of radiation whose energy is far from the absorption edges as known as the extinction rules. They can nevertheless be “switched on” close to an absorption edge, due to the anisotropy of the resonant tensor of scattering. Resonant “forbidden” reflections have been studied in many crystals. However, the resonant forbidden reflections for an aperiodic crystal has never been observed yet. The objective of this study is to measure the forbidden reflection for aperiodic crystals. In this study, the Al-Cu-Rh (Al58Cu38Rh4) quasicrystal is focused as an aperiodic crystal.