Electron Emission and Diffraction by a Copper Crystal

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Abstract
Correlation between changes in slope of secondary electron curve, and position of diffraction beams.—A narrow beam of electrons of variable speed is incident normally on the (100) face of a copper crystal. Measurements of the total secondary electron current are obtained under the same conditions as the angular distribution of scattered electrons for bombarding potentials from 0 to 250 volts, and after the crystal has been thoroughly degassed at red heat in an exceptionally good vacuum. The total secondary electron curve shows two maxima at 3 and 10.5 volts, respectively, and many sudden changes in slope in the region between 10.5 and 250 volts. Intense beams of full-speed electrons are found to issue from the crystal at such voltages as to account for the maxima, and for many of the changes in slope. Other beams are to be expected in the direction of the normal to the crystal, and hence are outside the solid angle of observation; they, however, contribute to the total secondary current, and appear sufficient to account for the remaining changes in slope. It thus appears that changes in the electron emission at potentials corresponding to energy levels within the atom are, at most, relatively unimportant in the production of sudden changes in slope in this region.