The probability of PE – rule of 3s:
- Incidence Electron must have enough energy to overcome the binding energy:
- Classic Example: 33.0 keV photon will NOT be able to lose the 33.2 keV K shell electron iodine. (it might knock loose the L or M – but not the K).
- PE is MOST likely to occur near the binding energy (assuming its greater)
- Classic Example: 34.0 keV photon is more likely to knock loose the 33.2 keV K shell electron from iodine, relative to a 100 keV phonon.
- In FACT! This is described in a highly tested way:
- PE Probability ~ 1 / Energy Cubed Or 1/KvP^3
- The tighter the electron is bound the more likely the PE
- Tighter bound electrons live in higher Z atoms
- The K shell is actually favored in lower Z atoms because it is most tightly bound
- Classic Testable Math:
- PE Probability ~ Atomic Number Cubed