Stimulated Emission of Bremsstrahlung

Stimulated emission of radiation from atoms or molecules is the process by which a maser operates. All masers use the transitions between bound states for their operation. However, it is also well known that radiation can be emitted from a free electron in the presence of a static electric or magnetic field. The presence of this static field--for example the field of a nucleus--is necessary to simultaneously conserve energy and momentum during the emission or absorption process. Free electrons far from any other field can neither emit nor absorb photons of an infinitely extending radiation field because if they did, conservation of energy and momentum would be violated, as can easily be shown. Free electrons can only scatter photons, a phenomenon known as the Compton effect. The emission of radiation from an electron passing by a nucleus is 1557 1570 TIIE B E L L SYSTEM TECHNICAL J O U R N A L , S E P T E M B E R 1902 known as Bremsstrahlung. It will be shown in this paper that stimulated emission of Bremsstrahlung is possible if the incident electron travels more or less parallel to the electric field vector of the stimulating radiation field. The electron absorbs radiation if it travels more or less perpendicular to the electric field vector of the stimulating field. Since stimulated emission of Bremsstrahlung exists, amplifiers and oscillators may be constructed using this effect. Stimulated emission of Bremsstrahlung does not require any bunched electron beams or observation of phase relationships.