Pair production

In physics, pair production can happen when a photon with a lot of energy is near the nucleus of an atom. This most commonly makes an electron and a positron. It can also make other subatomic particles, but it has to make the antiparticle (opposite particle) of that subatomic particle too. The two particles go in opposite directions. 

y: photon 
e+ is positron and e- is normal electron.

The minimum required is 1.022 MeV (twice the rest mass energy of an electron).
Pair production is more common if the photon has a lot of energy. It is also more common if the nucleus has a bigger atomic number. Pair production usually happens with energy levels over 25 MeV. Pair production happens sometimes in radiation therapy treatments that use photon beams with a lot of energy.
It is somewhat related to photoelectric effect. 

Category:Nuclear physics
Category:Antimatter