The Kα3,4 satellite spectra, originating in the [1s2p]−1→ [2p]−2 transition, were measured with high resolution for Co and Fe, using photoexcitation by tunable monochromatized synchrotron radiation. Fits to a phenomenological sum of Voigt functions and to ab initio relativistic Dirac–Fock-calculated spectra resolved the structure underlying the spectra. The dependence of the satellites' intensity on the excitation energy yielded accurate values for the excitation thresholds. The shake-theory-based Thomas model was found to deviate from the measured intensities, indicating near-threshold major contributions from non-shake excitation processes, such as the knockout, or ‘two step one,’ effect.
