User:Lundberg09/Resonant Inelastic X-ray scattering

Resonant Inelastic X-ray Scattering (RIXS) is an X-ray spectroscopy technique used to investigate the electronic structure of molecules and materials.

Overview
Resonant inelastic X-ray scattering is a photon-in photon-out process. An X-ray photon scatters off a target, while at the same time transferring energy and momentum. By monitoring both the incident and emitted photons, the amount of energy transfer can be measured as a function of incident energy. The amount of energy transfer is coupled to fundamental processes in the target material. RIXS therefore gives detailed information about the electronic structure. The process can also be described as a resonance X-ray Raman process.

A simplified interpretation of the RIXS event can be made by imagining a two-step process. Starting from the initial state, absorption of an incident photon leads to creation of an excited intermediate state, typically a core hole. From this state, emission of a photon leads to the final state. The absorption process gives information of the unoccupied orbitals, while the emission gives information about the occupied orbitals. In the RIXS experiment these two pieces of information are also directly correlated.

The natural linewidth of a spectral feature is determined by the lifetimes of initial and final states. In X-ray absorption and emission spectroscopy, the resolution is often limited by the relatively short life time of the core hole. In RIXS the lifetime of the final state is longer than the lifetime of the intermediate state, which leads to sharp spectra in the energy transfer direction. At the same time, RIXS experiments keep the advantages of the X-ray probe, e.g., element specificity.

In contrast to elastic X-ray scattering, radiative inelastic X-ray scattering is a very weak process. RIXS experiments therefore require a high-brilliance X-ray source, and are only performed at synchrotron radiation sources. RIXS studies can be performed using both soft and hard X-rays.

Applications

 * High-temperature superconductors, e.g., cuprates.


 * Metalloproteins, e.g., the oxygen-evolving complex in Photosystem II.


 * Catalysis, e.g., zeolites.


 * Liquid water.