BetheHeitlerProzess
Bethe-Heitler process, named after Hans Bethe and Walther Heitler, is the production of an electron-positron pair when a high-energy photon interacts with the electromagnetic field of a nucleus. It is a fundamental gamma-ray interaction in matter described by quantum electrodynamics. The reaction requires photon energy above 1.022 MeV (twice the electron rest mass) and results in an electron, a positron, and a recoiling nucleus. The probability grows with the square of the nuclear charge Z and depends on energy, with corrections from screening by atomic electrons and from nuclear recoil.
In the simplest case the photon converts to a pair in the field of the nucleus, preserving
Historically, Bethe and Heitler formulated the cross section for this process in 1934, with subsequent refinements