Resonance Auger and autoionization processes in solid lanthanum after 4d to 4f resonant excitation by synchrotron radiation

The decay processes of metallic La after resonant 4d - > 4f excitation by synchrotron radiation have been studied by means of electron spectroscopy. Excitation to the 4d exp 9 4f exp 1 ( exp 3 D sub 1 ) state, which is below the 4d ionization threshold, was found to decay predominantly through N sub 4,5 O sub 2,3 O sub 2,3 and N sub 4,5 O sub 2,3 V spectator resonance processes. The energy shift relative to the corresponding normal Auger energies was 1.6 plus/minus 0.3 eV in the case of NOO resonance Auger decay, whereas no energy shift was found for the NOV Auger electrons. The excitation to the main 4d - > 4f giant resonance was found to decay through ionization leading to a one-hole final state 5s exp --1 or 5p exp --2 , or through normal Auger processes. Autoionization processes are strong on the low energy side of the resonance, but when the excitation energy increases, normal Auger processes become more and more dominant, indicating a change in the nature of the giant resonance.