Separation of two-electron photoexcited atomic processes near the inner-shell threshold.

By means of a high resolution resonant inelastic x-ray scattering spectroscopy, we have for the first time separated spectral features pertaining to different two-electron atomic processes in the vicinity of an inner-shell threshold. Contributions of shakeoff, shakeup, and resonant 1s3p double excitations were extracted from the Ar KM-M{2,3}M x-ray satellite line intensity measured as a function of photon energy from [1s3p] double excitation threshold to saturation. The isolated [1s3p]nln'l' excitation spectrum is critically compared to the outcome of the multiconfiguration Dirac-Fock model with relaxation.