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

Abstract

Abstract. 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 determinations, the impact on magnetic X-ray scattering, but also resonant Raman scattering and nuclear resonant scattering. However, many aspects of resonant elastic X-ray scattering (REXS) were still being revealed 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 theoretical 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.

REXS contribution to electronic ordering investigation in solids

“…As extensively discussed by other authors in these same special topic issue [1,2], resonant X-ray techniques provides a core-hole spectroscopy point of view on matter. This immediately implies synchrotron specificity, due to the need to tune the impinging radiation (photon-in) energy to excite an electronic inner shell resonance.…”

“…In some cases, due to the subtlety of the effects investigated and the advanced tensorial analysis required, this process has been subject to controversial attributions for quite a while. After pioneering theoretical studies concomitant with the discovery of RXD (see citations in [1]), a number of authors has contributed to the development of the RXD formalism in various ways [40][41][42][43][44][45][46][47][48][49][50][51], effectively combining spectroscopic and diffractive information together.…”

Probing a crystal's short‐range structure and local orbitals by Resonant X‐ray Diffraction methods

“…. In 2012, further reviews appeared on the occasion of the Resonant Elastic X‐ray Scattering workshop 2011 concerning the development within the last 20 years in general and with specific focus on actinide systems , theoretical aspects as well as polarization analysis .…”

High energy resolution off-resonant spectroscopy: A review

“…In principle, RXES combines the aspects of simultaneous probing of occupied and unoccupied electronic states in a single experimental approach. In general two X-ray scattering processes may be distinguished for resonant X-ray-matter interaction: Resonant elastic X-ray scattering (REXS) [65,66] and Resonant inelastic X-ray scattering (RIXS) [67,68]. The REXS process delivers information on the spatial modulations of charge, spin and orbital degrees of freedom, whereas the RIXS process provides data on the density of unoccupied electronic states and the geometric orientation of the interacting atoms.…”