Electron Diffraction by Transmission through Thin Liquid Films

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Abstract
Electron interference has been obtained by the transmission of 50‐kv electrons through thin liquid films of the silicones: DC703, DC500, and DC200; and the hydrocarbons: octoil, castor oil, and glycerine. A commercial electron microscope (RCA, type EMU) was used after modification of the specimen holder. The electron diffraction patterns obtained from the hydrocarbons were all practically the same. They were characterized by three complete diffraction halos. The Bragg spacings (d) for octoil were found to be 4.93A, 2.26A, and 1.23A. These distances compare closely with values obtained previously for electron diffraction in liquid phytol (C20H39OH), Nujol, and Cenco pump oil. The patterns obtained for the silicones were significantly different from those of the hydrocarbons. Four complete rings were observed for DC703, giving d values of 8.17A, 4.18A, 1.97A, and 1.27A. The DC500 and DC200 fluids showed only three rings with Bragg spacings of 7.40A, 3.96A, and 1.27A; the ring which occurred at d=1.97A for DC703 was absent. The accepted Si–O distance of 1.60A is in agreement with the above data; however, the Si–O–Si–O angle is found to be approximately 104°. Such conclusions were confirmed by density calculations.

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