Auger resonant Raman studies of atoms and molecules

Many important results in the field of excitation and decay of a core hole in an isolated atom or molecule have recently been obtained under the so-called Auger resonant Raman conditions. When the bandwidth of the exciting radiation is narrower than the core hole lifetime broadening of the neutral core-excited state, it is not possible to disentangle the excitation/de-excitation processes in a two-step framework, but the whole phenomenon should be considered as a scattering process and treated in a one-step picture. Such experimental observations have recently become feasible with state-of-the art light sources (such as undulator beam lines at synchrotron radiation facilities) and high-resolution electron energy analyzers. The main results achieved in the early days included line narrowing and linear energy dispersion of spectral features related to the final states of the electron decay. More recently, other interesting findings such as lifetime/vibrational interference, detuning effects, non-linear dispersion, fragmentation dynamics etc., have been investigated in great detail. A general overview is presented here, with emphasis on the experimental aspects.