^Pair production

Actually 1.02 MeV is the rest mass energy of a pair of Electron & positron. If the energy of photon striking the nucleus is greater than 1.02 MeV, then this excess energy is shared equally by the Electron & positron as the KE. Pair production effect can’t take place in vacuum. As it is impossible for pair production effect to conserve both energy & momentum if it take place in vacuum.