RIXS is an electronic scattering process involving the excitation of a system, in its initial (often electronic ground) state, to a core-excited intermediate state followed by decay into a final state . The RIXS channel were the final state is the same as the initial state corresponds to elastic scattering, whereas inelastic scattering involves differences in electronic or nuclear degrees of freedom of the initial and final state wave functions. Hence, with sufficient energy resolution, RIXS can be used to study many kinds of excitation processes with an energy selectivity created by the intermediate coreexcited state, which is targeted by tuning the energy of the incoming photons .