Abstract
Proton resonance in crystal water of Mg(H2O)6Cl2, Mg(H2O)6Br2, CaI26H2O, SrI26H2O and MgI28H2O was studied in temperature range from −90°C to +110°C and the same in CaCl26H2O, CaBr26H2O, SrCl26H2O and SrBr26H2O was studied in the range above room temperature, all in powdered states. Line shapes were recorded by the radiofrequency spectrometer with an automatic field scanning apparatus connected to the sweeping coils of a permanent magnet. Transitions of second moment and line shapes were observed for all the above salts. Experiments on single crystals of Mg(H2O)6Cl2 and CaI26H2O were also carried out at room temperature. In Mg(H2O)6Cl2, Mg(H2O)6Br2, CaI26H2O, SrI26H2O and BaI26H2O, water molecules of hydration have the states of hindered rotational motion below melting point, but in CaCl26H2O, CaBr26H2O, SrCl26H2O and SrBr26H2O, these rotational states were not observed. The angle between the rotational axis of a water molecule and its inter-proton direction was estimated to be about 90° in the case of Mg(H2O)6Cl2. In the cases of CaI26H2O and SrI26H2O these angles are calculated to be 45° or 60°, and these results suggest the precession of the rotational axis, if rotational motion of water molecules is assumed to occur about an axis perpendicular to the inter-proton axis. Sharp peaks appearing in chlorides and bromides of Ca and Sr are interpreted as the narrowing due to random re-orientation of the rotational axis.
