RESONANCE AUGER AND AUTOIONIZATION PROCESSES IN SOLID LANTHANUM AFTER 4D-]4F RESONANT EXCITATION BY SYNCHROTRON RADIATION

The decay processes of metallic lanthanum after resonant 4d --> 4f excitation by synchrotron radiation have been studied by means of electron spectroscopy. Excitation to the 4d9 4f1(3D1) state, which is below the 4d ionization threshold, was found to decay predominantly through N4,5O2,3O2,3 and N4,5O2,3V spectator resonance processes. The energy shift relative to the corresponding normal Auger energies was 1.6 +/- 0.3 eV in the case of NOO resonance Auger decay, whereas no energy shift was found for the NOV resonance Auger electrons. The excitation to the main 4d --> 4f giant resonance was found to decay through autoionization leading to a one-hole final state 5s-1 or 5p-1, 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.