|Pair production results in the conversion
of a gamma-ray photon into an electron-positron
pair within the Coulomb field of the nucleus. The interaction is with
the atom as a whole.
The process of pair production is only possible
if the incident gamma-ray photon energy exceeds twice the combined
rest mass energy of the electron and positron pair (1022 keV).
- Ee + Ep
- 1022 keV
The ejected positron will inevitably meet a free electron and
annihilate, releasing two 511 keV gamma-rays.
Use the simulation opposite to
investigate pair production.
The energy absorbed by during the process of pair production can be observed
as the pair
production peak in the detected energy
spectrum. One example of a radionuclide that produces a 511 keV photon is 22Na.