pair production

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The simultaneous creation of a subatomic particle and its antiparticle from another form of energy, especially the production of a positron and an electron from a gamma ray photon in a strong electric field, such as that surrounding a nucleus.

from the GNU version of the Collaborative International Dictionary of English.

• (Physics) The simultaneous creation of a particle and its antiparticle, such as an electron and positron, from a photon; -- usually due to its interaction with the strong field near a nucleus.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the transformation of a gamma-ray photon into an electron and a positron when the photon passes close to an atomic nucleus