Electron Diffraction Study of the Hydrogen Bonds in Boric Acid

Abstract

IN recent years the techniques of X-ray diffraction structure analysis have been refined to such an extent that, with careful work, the positions of hydrogen atoms in a structure may be determined when each hydrogen atom is bound to a single atom. The detection of a hydrogen ion in a hydrogen bond, however, is a much more difficult task, since only a fraction of an electron can be considered as localized near the proton. This amount of ionization reduces the atomic scattering factor for X-rays. However, the atomic scattering factor for electrons is correspondingly increased since this is given by ɛ = (Z − ƒ)λ²/sin²θ, where Z is the atomic number, ƒ is the X-ray scattering factor, λ is the effective wave-length of the electron beam and θ is the Bragg angle. Hence, hydrogen ions in hydrogen bonds should be detected more readily in structure analyses based on electron diffraction data. Techniques for structure analysis using single-crystal electron diffraction patterns have been evolved and will be described elsewhere. They have been applied to the study of the structure of boric acid layers.