Auger decay/electrons intensity

The profiles for most segregants, characterised by a rapid exponential decay with depth etched, are compatible with a single atom layer of segregant atoms at the fracture plane. The decay of the Auger electron intensity, /A, for the sputtering of atoms at the fracture plane is described by ... 

For excitation routinely monochromatic x-ray sources are used, also in this work a twin-anode setup with a Mg Ka (1253.6 eV) and Al Ka (1486.3 eV) source is applied. Generally, the intensity of the electrons A (E) as a function of kinetic energy is measured however more often XPS spectra are plotted versus the BE. Other than the desired photoelectron peaks in a XPS spectrum, peaks originating form Auger decays are observed as a result of the mechanism introduced in the previous subsection. As a convention, photoelectron peaks are labeled according to the quanmm number of the level (see previous AES subsection) from which the electron originates [39, 81]. 

As previously discussed, according to the Fermi golden rule, the intensity of processes like photoemission and Auger decay is expressed by a transition matrix element between initial and final states of the dipole and, respectively, the Coulomb operator. In both cases the final state belongs to the electronic continuum and we already observed that an representation lacks a number of relevant properties of a continuum wavefunction. Nevertheless, it was also observed that the transition moment, due to the presence of the initial bound wavefunction, implies an integration essentially over the molecular space and then even an l representation of the final state may provide information on the transition process. We consider now a numerical technique that allows us to compute the intensity for a transition to the electronic continuum from the results of I calculations that have the advantage, in comparison with the simple atomic one-center model, to supply a correct multicenter description of the continuum orbital. 

As discussed in previous sections, the expression of the intensity for any ionization process always involves a continuum orbital, which may describe the photoelectron in XPS or the secondary emitted electron in Auger decay. In the one-center model the problem is overcome by approximating the molecular continuum orbital by an atomic continuum orbital and finally recurring to available or more easily computable atomic transition moments and two-electron integrals. We have also discussed how the multicenter character of the continuum orbitals can be correctly described by... 

Time-resolved measurements of photogenerated (very intense illumination, up to 0.56 GW/cm ) electron/hole recombination on CD (selenosulphate/NTA bath) CdSe of different crystal sizes has shown that the trapping of electrons, probably in surface states, occurs in ca. 0.5 ps, and a combination of (intensity-dependent) Auger recombination and shallow-trapped recombination occurs in a time frame of ca. 50 ps. A much slower (not measured) decay due to deeply trapped charges also occurred [102]. A different time-resolved photoluminescence study on similar films attributed emission to recombination from localized states [103]. In particular, the large difference in luminescence efficiency and lifetime between samples annealed in air and in vacuum evidenced the surface nature of these states. 

In summary, the dynamics of the electronic decay of inner-shell vacancies in a charged environment, such as created by interaction of a cluster with a high intensity FEL radiation, can be qualitatively different from the one induced by a low-intensity source. If the emitted electrons are slow enough to be trapped by the neighboring charges, the familiar exponential decay will be suppressed by quantum beats between the initial state and the quasi-continuum of discrete final states. Physically, the predicted oscillations correspond to creation of the initial vacancy due to the reflections of the emitted electron by the charged cluster potential and the subsequent inverse Auger transition. 

---