Auger decay relaxation spectra

We have tacitly assumed that the photoemission event occurs sufficiently slowly to ensure that the escaping electron feels the relaxation of the core-ionized atom. This is what we call the adiabatic limit. All relaxation effects on the energetic ground state of the core-ionized atom are accounted for in the kinetic energy of the photoelectron (but not the decay via Auger or fluorescence processes to a ground state ion, which occurs on a slower time scale). At the other extreme, the sudden limit , the photoelectron is emitted immediately after the absorption of the photon before the core-ionized atom relaxes. This is often accompanied by shake-up, shake-off and plasmon loss processes, which give additional peaks in the spectrum. 

Mdssbauer spectrometry gives information about the chemical environment of the Mdssbauer nuclide in the excited state at the instant of emission of the photon. It does not necessarily reflect the normal chemical state of the daughter nuclide, because of the after-effects that follow the decay of the mother nuclide (recoil and excitation effects, including emission of Auger electrons). At very short lifetimes of the excited state, ionization and excitation effects may not have attained relaxation at the instant of emission of the y-ray photon this results in a time-dependent pattern of the Mdssbauer spectrum. 

The Cu Lu XES data (44,45) shown in Figure 4 dramatically reveals the switch in character of the 1 and 2 v states between CuO and 123. As in the Auger process, the satellite cd initial state relaxes to the cp state before the decay, and the x-ray emission process is intra-atomic in nature. Therefore, the XES reflects primarily the dp DOS. In CuO the XES spectrum peaks at 3 eV, in the 123 it falls around 4.2 eV, very near where we indicated the dp states fall in the UPS data. The large Intensity in the CuO XES extending above the Fermi level is believed to be an experimental surtifact ( ). 

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