X-ray fluorescence and Auger-electron coincidence spectroscopy of vacancy cascades in atomic argon

Argon L-2,L-3-M2,3M2,3 Auger-electron spectra were measured in coincidence with K alpha fluorescent x rays in studies of K-shell vacancy decays at several photon energies above the K threshold and on the 1s-->4p resonance. The complex spectra recorded by conventional electron spectroscopy are greatly simplified when recorded in coincidence with fluorescent x rays, allowing a more detailed analysis of the vacancy cascade process. The resulting coincidence spectra are compared with Hartree-Fock calculations, which include shake-up transitions in the resonant case. Small energy shifts of the coincident electron spectra are attributed to postcollision interaction with 1s photoelectrons.