Reflection of Electrons by Standing Light Waves: Experimental Study

Abstract

The reflection of electrons by standing light waves, i.e., the stimulated Compton scattering predicted by Kapitza and Dirac, has been studied experimentally. It has been found that the electron scattering observed in a preliminary study was spurious. Subsequent experiments were performed with greatly improved circuitry and augmented laser intensity. Deflections suffered by 1.6-kV electrons traversing the intense radiation field in the cavity of a giant-pulse laser were measured directly. In many dozens of experiments, electrons were observed to recoil at roughly the expected Bragg angle and with a probability of the predicted order of magnitude. The limited resolving power of the experiment and the uncertainty in the spatial distribution of laser intensity prevented an unequivocal verification of the Kapitza-Dirac theory. It was also found that the electron beam experienced an appreciable field when the laser pulse struck certain parts of the cavity wall. This field took a significant time to develop and sometimes exhibited erratic fluctuations over a period of dozens of microseconds after the laser pulse abated.