Interplay of complex decay processes after argon 1s ionization

Complex decay pathways involving radiative and nonradiative relaxation after deep core-level ionization in argon are disentangled by a unique combination of several synchrotron radiation-based spectroscopic techniques. In particular, by comparing the results obtained from electron-ion coincidence, photon-ion coincidence, and x-ray emission measurements, we are able to distinguish the final ionic states produced in the cascade decay involving $K\ensuremath{\alpha}$ and $K\ensuremath{\beta}$ radiative decay and final ionic states produced by nonradiative cascade decay. High-resolution Auger electron spectroscopy is then used as a complementary tool to identify the $LMM$ transitions contributing to the cascade decay. Ab initio calculations are performed to identify the electronic states involved in the $LMM$ decay.