The reflection of electrons from standing light waves

Abstract

Experiments are described in which a slow electron beam is deflected by a standing light wave produced by a high intensity laser. This interaction is believed to occur as a Bragg reflection of the electrons in the standing wave intensity pattern set up in the light beam, as was predicted byKapitza andDirac in 1933. No energy interchange takes place but a momentum transfer which results in a Bragg relationship for the angle of reflection. The probability is proportional to the square of the light intensity.Kapitza-Dirac's original particle treatment of the effect is shortly reviewed and a wave mechanical treatment is added. Two types of experiments A and B are described. In type A an electron beam is scanned through a standing light wave and any deflection is detected with a differential amplifier. In type B the electron beam is locked in at maximum deflection and the laser output is simultaneously displayed with the deflected electrons on a fast dual beam oscilloscope. The electron beam deflections follow the fine structure of the laser spikes. Results from both types of experiments stay within the right magnitude of the theoretical predictions.