ON THE INTERPRETATION OF THE FINE-STRUCTURE BELOW AND ABOVE THE CU-M23VV AUGER LINE

In the last few years, an EXAFS-like meaning was attributed to the fine structure which is present above the shallow M23VV Auger line of 3d-transition metals. For a deeper understanding of the origin of such fine structure, we performed Cu-M23-Extended Energy Loss Fine Structure (EELFS) and Secondary Electron (SE) measurements from the cut-off, up to, and well above, the Cu-M23VV Auger peak on Cu(100), which is a test case for discriminating among possible contributions. We found that the SE-Fine Structure above the M23VV line has only a partial one-to-one correspondence with the EXAFS-like EELFS measurements above the M23-edge. On the contrary, the former is in a much better agreement with the Extended Bremsstrahlung Isochromat Fine Structure (EXIFS) taken from the literature. Reminding that EXIFS was interpreted in the EXAFS framework, the present study confirms the EXAFS-like meaning of the features observed above the Cu-M23VV peak but, in the meantime, shines some lights on the possible presence of two different overlapping contributions, the first starting at the SE-onset, and the second at the autoionization edge, which is close to the M23VV peak.