Trident pair production
$e^-\gamma \to e^-e^+e^-$
A photon converts to an electron-positron pair in the field of an electron. Called the trident process because three charged particles emerge. Important in strong-field QED and astrophysical environments.
Recently observed in the strong Coulomb fields of heavy nuclei. Closely related to the Bethe-Heitler process.
No diagrams cataloged for this process yet.