✍ Scribed by Mildred Allen
No coin nor oath required. For personal study only.
When an electron passes through a thin FOUNDATION film, there are three things which may Communicstioa No* M* happen to it : (a) It may suffer a change in direction without change in velocity, owing to a collision with a nucleus.
(b) It may suffer changes in velocity and in direction owing to collisions with other electrons; these may be large or small. (c) It may knock an electron out of an atom, thus ionizing that atom. To these three effects many now be added the diffraction effects without velocity change arising very vividly from its wave character as illustrated in the experiments of Davisson and Germer,' G. P. Thomson,2 Rupp 3 and others, and depending upon the crystalline arrangement of the atoms; these, however, will not be discussed here. The theoretical explanation of these various effects is not to be attempted in this paper. It will concern itself with the changes in velocity suffered by an electron in passing through a thin film, the variation in absorption of these electrons with the velocity of the beam and the thickness of the film, and the angular distribution of the transmitted electrons. When in connection with any of these problems an author has attempted to find evidence for the ionization of the atoms of the film, inasmuch as ionization by electrons has been very little investigated except for the case of gases, this will be pointed out together with whatever reasons are obvious for his failure to detect such evidence.
It will appear that, in spite of the enormous amount of experimental work which has been done on the transmission of electrons by thin films, the whole story has by no means been told with respect to such transmission.
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