Molecular structure as determined by a new electron diffraction method. I—Experimental

Abstract

In this and the following paper a method will be described of obtaining good high order interference photographs of electron beams scattered by the vapour of any stable substance, organic or inorganic, whose vapour pressure exceeds 10cm at 1000°C, as well as an interpretation of the results achieved with this improved technique, using a simplified method of calculation. The apparatus has been so developed that it is now as easy to obtain electron interference patterns of vapours as it is to make measurements of the Raman effect, dipole moment, infra-red and ultra-violet absorption spectra; the results enable us to clear up a number of doubts that still exist concerning the spatial structure of certain compounds. Debye and Ehrenfest showed theoretically that if a beam of monochromatic X-rays was passed through a gas consisting of randomly oriented polyatomic molecules with fixed interatomic distances, then an interference effect might be expected. Later Debye worked out the general case for a molecule containing 1- i - j - n atoms each having a scattering factor F.