Electron Diffraction at Multiple Slits

A glass plate covered with an evaporated silver layer of about 200 Å thickness is irradiated by a line-shaped electron probe in a vacuum of $10−4 Torr$⁠. A layer of polymerized hydrocarbon of very low electrical conductivity is formed at places subjected to high electron current density. An electrolytically deposited copper layer leaves these places free from copper. When the copper layer is peeled away a grating with slits free of any material is obtained. Slits 50 μ long and 0.3 μ wide with a grating spacing of 1 μ are obtained. The maximum number of slits is five. The electron diffraction pattern obtained using these slits in an arrangement analogous to Young's light interference experiment in the Fraunhofer region shows effects corresponding to the well-known interference phenomena in light optics.