Auger ionization

The radicals are produced by various processes, although little is known for certain. A major question exists as to whether the radicals are produced by the initial bond rupture - , by recoil impact , by Auger ionization , by gamma radiation damage or by normal exchange . ... 

If the pattern of yields obtained is similar to that observed through neutron bombardment, then Auger ionization can be eliminated as a necessary mode of excitation. (The reverse experiment is not so easily conceived.) An additional item of flexibility is added in the possible use... 

FlO. 2. Schematic representation of the types of y-cascade, showing the origins of (i) pure recoil, (ii) recoil followed by Auger ionization, and (iii) Auger ionization with little or no recoil. 

It is likely that the answers to these questions will come only from more selective and sophisticated experiments than have been done hitherto, although some useful directions have been established. The use of high-sensitivity electron spin resonance for the study in situ of anticipated radical species will likely be possible, if the background signals from other radiation-produced species are not too intense. Studies of the chemistry of implanted atoms and ions in solid organometallic substrates will make it possible to start with totally unbound atoms which suffer no Auger ionization and thus to simulate the extreme of the total recoil. Careful studies of the thermal annealing effects, especially in the presence of reactive atmospheres, will... 

Auger ionization In this case, an inner shell vacancy is filled by an electron from an outer shell and the excess energy instead of being emitted as a photon, is consumed in ejecting a second electron (called an... 

Coster-Kronig process This is a special case of Auger ionization in which the vacancy transition is... 

Autoionization This process is similar to Auger ionization. In this case a vacancy is created by promoting an inner shell electron to an outer bound level, instead of being ejected from the atom. When this vacancy is filled by an outer shell electron, if the difference in energy exceeds the ionization potential of any electron, then that electron is ejected leading to a singly ionized atom (Figure 6). 

The Auger processes compete with radiative decay. The probability of radiative decay is proportional to Z, whereas the probability of Auger ionization is constant, independent of Z. The fluorescence yield (o) is defined as the ratio of the number of vacancies filled by X-ray emission to the total number of vacancies (filled by all processes). For K shell, = number of K X-ray photons/ (number of K X-ray photon + number of Auger electrons) = a) where a = 1.12x10. Hence,... 

---