The natural widths of atomic resonances do not broaden spectral lines of emitted particles, which makes the corresponding spectroscopies suitable for high-resolution studies of x-ray absorption. While resonant inelastic x-ray scattering (RIXS) results in a narrow-band x-ray signal which primarily depends on the charge of the emitter, the resonant Auger (RA) emission is more dispersed and promises the separation of individual atomic resonances. To disentangle the $1s^{-1}3p^{-1}nl{n}^{\prime }{l}^{\prime }$ absorption spectrum in Ar, we have measured a sequence of $K{M}_{23}-L_{23}^2{M}_{23}$ RA spectra with a high experimental resolution. Although only parts of the RA spectra were reliably isolated due to the strong overlap with the intense $K-L^2$ Auger emission from ions, the data analysis shows contributions from separate groups of resonances to the Auger signal in greater detail compared to the previous high-resolution absorption and RIXS studies. The calculated differential cross sections are consistent with the available experimental results when the angular dependence of RA emission and the interference of absorption-emission paths through different resonances are accounted for.

• Received 17 May 2023
• Revised 22 September 2023
• Accepted 18 October 2023

DOI:https://doi.org/10.1103/PhysRevA.108.053113