A Test for Polarization of Electron Waves by Reflection

Abstract

A homogeneous beam of electrons is directed at 45° incidence against a /{111/}—face of a nickel crystal. The beam regularly reflected from this face impinges upon a second similar face at the same incidence angle. A Faraday collector is set to receive electrons regularly reflected from the second crystal, but only such electrons are accepted into the collector as have survived the two reflections without appreciable loss of kinetic energy. The collector and second crystal are rigidly joined, and may be rotated about the axis of the beam proceeding from the first to the second crystal. Measurements of the intensity of the twice reflected beam have been made at bombarding potentials from 10 to 200 volts. Within this range selective reflections (intensity maxima) are observed at 20, 55, 77, 103 and 120 volts. These five selectively reflected beams have been separately tested for polarization by measuring the current received by the collector as a function of the azimuth of the movable system. If electron waves are polarized by reflection the intensity of the twice reflected beam should be greatest when the planes of incidence of the two reflections coincide, and least when they stand normal to one another. No such variation of the current to the collector is observed within the limits of error of the measurements—about one half of one percent of the total current. Our observation is that electron waves are not polarized by reflection.