Resonant elastic X-ray scattering: Where from? where to?

摘要

The International Conference on Anomalous Scattering held in Malente, Germany, in 1992 examined the broad issue of 'dispersion or resonant scattering' for X-rays. The significant aspects discussed at that time included: the evaluation of X-ray scattering factors, the role of local broken symmetries and the application to structure determi-nations, the impact on magnetic X-ray scattering, but also resonant Raman scattering and nuclear resonant scattering. However, many as-pects of resonant elastic X-ray scattering (REXS) were still being re-vealed and soon it was realised that new productive paths of research would open up. In the last two decades, applications have developed thanks to concurrent developments in X-ray instrumentation and the-oretical approaches. Focusing on REXS only, noteworthy fields are: the observation of multiple order parameters, the detection of multipolar moments, but also applications in chemistry and materials sciences, macromolecules and soft matter in the soft X-ray range. REXS has evolved from the exploitation of large resonant signals to a powerful experimental and characterisation method aimed at unravelling new phenomena. The recent technical and theoretical advances have paved the way to further REXS developments in many fields of science.