Auger decay of 1s^-13p^-1nlnl doubly excited states in Ar

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)nln'l' absorption spectrum in Ar, we have measured a sequence of KM23 - (L23M23)-M-2 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.