ABSTRACT
This chapter introduces the electron-volt (eV), which represents the energy acquired by an electron having traversed a potential difference of 1 V. Nuclear physics at that time dealt with transmutations resulting from the interaction of beams of charged particles with matter. The available sources of ions were of two types: sources coming from the natural radioactivity of uranium, of which we have already spoken; more exactly, one used two descendants of uranium, radium and polonium, which exist in equilibrium with it; accelerators producing light ions, protons and deuterons having the desired energy. Joliot-Curie observed that this radiation induced emissions of protons in hydrogen media. To explain this phenomenon he invoked the Compton effect, that is, collision of a photon with a proton. The Compton effect, which results from interaction of the photons with atomic electrons, takes place all the time. In contrast, the proton Compton effect only takes place for extremely high energy.
