Wave packet dynamics from RIXS

One of the key features of resonant inelastic X-ray scattering (RIXS) is the evolution of the spectra when the excitation energy is tuned around a resonance. On resonance, the time scale for the signal generation in RIXS is given by the core hole life time. In the scattering duration time concept, detuning from the resonance adds an additional phase factor that leads to a suppression of signal from later times, effectively shortening the observed time scale.

In molecules this can be used as a variable stop watch to analyze nuclear and wave packet dynamics (oxygen: bond breaking in a jumpy way).

On solids, this principle has been successfully applied to the study of electron-phonon coupling rates. RIXS on solids can yield spectroscopic signatures that are very different with and without electron-phonon coupling. Comparing the ratio of both spectral signatures on the time scale of the core hole life time, gives then the electron-phonon coupling rate. By tuning the excitation energy around the resonance, the underlying stop watch can be varied independently from additional resonant effects.