Notice that the removal of the orbital electron established the environment for x-ray production and it is the expending of energy during the cascade that produces characteristic x-rays.Ĭharacteristic photons are created when orbital electrons of target atoms are removed from their shell and outer-shell electrons fill inner-shell vacancies. But any outer-shell electron can fill the K-shell vacancy it is just not as likely to do so. If a filament electron removes a K-shell electron from an atom, the most likely electron to fill the vacancy is an L shell because of proximity. Each time an orbital electron moves to a lower orbit, a characteristic photon is produced. ![]() This process of outer-shell electrons filling inner-shell vacancies continues down the line, creating a cascading effect called a characteristic cascade. This second vacancy is also filled by an outer-shell electron that again must give up some of its energy, producing another characteristic photon. Note that when the first orbital electron drops to fill the vacancy, it in turn leaves another. ![]() This energy is given off as a characteristic x-ray photon ( Figure 6-2). To do so the outer-shell electron must expend some of its potential energy. To correct this situation, outer-shell electrons drop to fill inner-shell vacancies. Recall from Chapter 2 that orbital shells fill from the shell nearest the nucleus outward and a vacancy in a shell makes the atom unstable. In general, a filament electron enters a target atom, strikes an orbital electron, and if its energy is greater than the binding energy of the orbital electron it is removed from orbit. Characteristic interactions involve the filament electron and an orbital electron of a target atom.
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