Diffraction of Electrons as a Search for Polarization

Electrons accelerated by voltages from 80 kv to 225 kv passed through a thin homogeneous foil of polycrystalline gold and formed a diffraction pattern on a fluorescent screen. Through a hole in the screen, various rays of the diffracted beam were made in turn to fall on a second diffracting foil similar to the first. The second diffraction pattern was obtained on a photographic plate and examined for any asymmetry that might be caused by polarization of the electron beam. After certain asymmetries in the apparatus were corrected, no asymmetry was found in the diffraction pattern. By interposing a vane for a given fraction of the time of exposure over part of the plate, a partial calibration of the plate could be obtained directly. It was estimated that if there was any asymmetry at all, it was certainly not above 10 percent and probably not above 5. From this result and the observations of other workers at voltages from 100 kv down, it seems safe to conclude that diffraction is wholly, or largely, ineffective in polarizing electrons with energies at any rate below 225 kv. This conclusion may be at variance with those of Rupp and Rupp and Szilard on double scattering and on scattering and diffraction of an electron beam. The relation of these different experiments is discussed.