One-step double autoionization into the double-photoionization continuum

We have determined the Fano parameters and oscillator strengths of the triply photoexcited Li 2s²2p ²P^o autoionizing resonance in the Li⁺ and Li²⁺ partial photoion yields. Using monochromatized photons we observed an asymmetric resonance profile not only in the Li⁺ but also in the Li²⁺ partial cross section. The interaction between the triply excited state and the double-photoionization continuum takes place via a one-step double autoionization, since a two-step autoionization of the discrete state is energetically not possible. Our theoretical calculations using an R-matrix method for both the Li⁺ and Li²⁺ partial cross sections show resonance profiles in good agreement with experimental result.