Characteristic x-rays
From MedPhysWiki
- Characteristic x-rays result from Coulomb interactions between the incident electrons and atomic orbital electrons of the target material (collisional loss).
- In a given Coulomb interaction between the incident electron and an orbital electron, the orbital electron is ejected from its shell and the resulting orbital vacancy is filled by an electron from a higher level shell.
- The energy difference between the two shells is:
- Either emitted from the target atom in the form of a photon referred to as characteristic photon.
- Or transferred to another orbital electron that is ejected from the target atom as an Auger electron.
- Characteristic photon and Auger electron eKLM following a vacancy in the atomic K shell.
- Energy of K photon: NEED TO UPLOAD IMAGES AND INSERT Slide 15
- Energy of eKLM Auger electron:NEED TO UPLOAD IMAGES AND INSERT Slide 15
- The fluorescent yield ω gives the number of fluorescent (characteristic) photons emitted per vacancy in a shell ( 0 ≤ ω ≤ 1) and ranges from 0 for low Z atoms through 0.5 for copper (Z = 29) to 0.96 for high Z atoms for K-shell vacancies that are the most prominent sources of characteristic x-rays.
- The photons emitted through electronic shell transitions have discrete energies that are characteristic of the particular target atom in which the transitions have occurred; hence the term characteristic radiation.
