Auger yields

The Auger effect is analogous to the internal conversion in that an atomic electron is emitted instead of the expected X-ray. Very little is well known about Auger yields in these transitions out beyond the K shell, and a more detailed discussion is outside the scope of this review. 

A core-ionized atom has two possibilities to lower its energy, namely Auger decay and X-ray fluorescence (described in more detail in Chapter 7). The Auger yields for processes following core hole creation in the K and L shell are sketched in Fig. 3.25 (right). Obviously, Auger processes are the dominant decay mode in light elements. 

Quantitative analysis of Auger spectra is quite possible, but less straightforward than in XPS. The main reason is that the effective intensity of primary electrons in the sample may be higher than that of the primary beam, because of backscattering effects. For example, the Auger yield measured from a thin film of... 

After these preliminaries, the partition into radiative (subscript R) and non-radiative (subscript A for Auger) transitions for the ls-hole decay in neon can be given in terms of intensities /R and /A or partial transition rates PR and PA by introducing a fluorescence yield coR and an Auger yield oja defined by... 

As a consequence of the two-step model for photoionization and subsequent Auger decay, there is a factorization of all observables. For the intensity, the product between the photoionization cross section angular distribution parameter fiA one has [BKa77]... 

The dynamics are contained in the photoionization cross section <7ph(2p3/2), in the Auger yield oja(L3-M1M1) and in the angular distribution parameters j ph(2p3/2) and j9A(L3-M1M1) of the non-coincident photo- and Auger electrons (see Section 5.2). For convenience, a ratio r is used in equ. (4.86b) which, however, is not a new parameter since in the present case it depends on j9A(L3-M1M1) (see equ. (8.133g)) ... 

According to the Auger yield Auger electron provided one scans over pass2 of the coincident Auger electrons (see Fig. 10.6). This yields the area Atrue of true coincidences (see equ. (10.65e))... 

Figure 9.7. Fluorescence yield co and Auger yield 1 - co for the K and L shells as a function of the atomic number. (According to E. H. S. Burshop The Auger Effect and other Radiationless Transitions. Cambridge University Press, London 1952.)...

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