Pair Production
Can happen if Eg > 1.022 MeV = 2 * m0(e-)
Rapidly increasing cross-section > 1.022 MeV
Stopping power/atom varies as Z2
Energy transferred is (hn - 1.022) MeV
Scattering nucleus plays fairly passive role(not much momentum transferred to nucleus)
Generally the positron gets annihilated, giving off another pair of 0.511 MeV photons. These generally escape and are not part of the absorbed energy