Physicists refer to the Compton effect, as the collision of a photon with a charged particle usually an electron. When the charged particle is much heavier, which is the case of a proton, the kinematics of the collision is such that the photon must have a very high energy for communicating a kick such as the one observed by Frederic and Irene Joliot-Curie . In the 1930s, there was not known sources of gamma of 50 million electron volts. Typically, the energies of gamma emitted by the nuclei are of the order of one million electron volts or less.