Resonant Inelastic X-ray Scattering
Resonant inelastic x-ray scattering (RIXS): this versatile x-ray spectroscopy is a combination of x-ray absorption and x-ray emission (see this review paper https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.83.705 ). It is based on the resonant absorption/emission of x-rays and therefore chemically sensitive to specific ions in matter. This versatile probes can measure at the same time localized excitations like crystal field or charge transfer excitations and momentum resolved collective excitations (magnons and phonons e.g.).
The development of X-ray free electron lasers as large scale facilities (SwissFEL at PSI, LCLS at SLAC Stanford, …) makes it possible now to do time-resolved pump-probe RIXS using X-ray pulses.