Auger electron emission process

Fig. 14. Schematic of the Auger electron emission process induced by creation of a K level electron hole.

Figure 18 The Auger electron emission process is a three-electron process involving both core and valence-level electrons...

Figure 5.16. Scheme of the Auger electron emission process. 

Figure 8.21 The competitive processes of X-ray fluorescence (XRF) and Auger electron emission...

An alternative mechanism of excess energy release when electron relaxation occurs is through x-ray fluorescence. In fact, x-ray fluorescence favorably competes with Auger electron emission for atoms with large atomic numbers. Figure 16 shows a plot of the relative yields of these two processes as a function of atomic number for atoms with initial K level holes. The cross-over point between the two processes generally occurs at an atomic number of 30. Thus, aes has much greater sensitivity to low Z elements than x-ray fluorescence. 

Fig. 2.1. Schematic diagram of electron emission processes in solids. Left side Auger process, right side photo-...

Fig. 16. Processes involved in Auger electron emission during X-ray photoelectron spectroscopy.

Fig. 1. Comparison of the four different physical processes which can be observed during the interaction of X-ray photons with matter 2 1. The two phenomena scetched below, namely photoelectron emission and Auger electron emission, can be detected and measured in a photoelectron spectrometer by determining the kinetic energy of the ejected free electrons...

The discussion above has considered only what happens to the electron that is removed from an inner shell. An atom with an inner-shell electron removed is unstable, and an electron from a higher orbital will soon fill the inner-shell void. Therefore, the energy difference between these two orbitals must be emitted by the atom (called a secondary process). This can occur by two competing processes (a) emission of a fluorescent photon or by (b) Auger electron emission (Stohr, 1992 pll6). If the atom in question is at a surface, the energy of the Auger electron can... 

There are other electron emission processes which lie between such well-defined limiting cases, e.g., resonance affected two-electron emission which lies between direct double photoionization and photon-induced two-step double ionization (photoelectron and Auger electron emission). 

The following examples focus on valence level ionization by ultraviolet light, since such processes would produce low energy electrons, which are the most effective at inducing reactions in an adsorbed molecule. There are also many examples of spin-polarized photoemission and Auger electron emission from core levels of both magnetic and nonmagnetic materials [29-35]. 

A variety of processes may take place at this stage, distinguishing the different techniques — photoelectron emission, Auger electron emission, ion emission, energy loss due to core-hole, plasmon or phonon excitation, as well as... 

From the point of view of obtaining surface structure information, the nature of this primary process is important in two ways. First, the process may be atom-specific, giving chemical selectivity, as in photoelectron emission and Auger electron emission. Second, the process can affect the characteristics of the outgoing particles, especially in terms of angular distribution, and in terms of the exact location within the surface where this primary process takes place. The angular distribution can give direct evidence of the molecular orientation with respect to the surface this happens, for instance, when an electron is emitted from a valence orbital. 

In section 2.3 we have decomposed various surface-sensitive techniques into a small set of more elementary processes. In this section we shall present appropriate formalisms that describe these individual processes. Namely, we shall discuss the theoretical treatment of the propagation of electrons in the surface region, as well as the treatment of elastic and inelastic electron-atom scattering, photoelectron emission and of Auger electron emission. These parts... 

The transition matrix element needed to describe Auger electron emission corresponds to the process in which an electron is ejected as a result of the filling of a deeper lying empty level by another electron. This process can be localized on one atom or involve neighboring atoms, especially if valence and conduction levels are involved. The Auger matrix element is/84/... 

FIGURE 3. Ionization, shaking and orbital rearrangement processes of the F ion in a fluoride at the time of Auger electron emissions. 

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