The Čerenkov Effect

Abstract

In 1934 P.A. Čerenkov performed a series of experiments on the luminescence emitted by certain liquid solutions, if irradiated with gamma rays deriving from radioactive sources. During the experiments, which continued until 1938, Čerenkov realized that the gamma rays cause a very weak electromagnetic radiation, even in pure solvents such as water and benzene, resulting in a dim blue light. However, an in-depth analysis of the physical properties of the emitted light revealed that the observed effect could not be a luminescence phenomenon. In first place, the Čerenkov radiation was emitted along a cone of directions forming a well-defined angle with the direction of the incident gamma rays and, in second place, the radiation was linearly polarized , and, in fact, none of these properties are inherent in luminescence. In addition, the observed radiation had universal character, in that these distinctive features were independent of the specific properties of the solutions used, such as their temperature and chemical composition.