An upper limit to the electric dipole moment of photons

Abstract

Abstract Two experiments are described which set upper limits to the longitudinal electric dipole moment of photons emitted in radioactive decay. The Mössbauer effect enables small changes of energy, which might result from the interaction between the photons and a varying electric field, to be looked for and the 14.4 kev transition in iron-57 has been used for this purpose. Two possible types of interaction are considered and, depending upon which approach is used, upper limits of 1.0 × 10−20 e.s.u. and 1.1 × 10−19 e.s.u. (95% probability) are established.