抄録
The shape of proton magnetic resonance absorption line in hydrogen perchlorate monohydrate was observed. The line was found to be simple and narrow at the room temperature, and to show the complicated structure corresponding to “three proton system” at the temperature below 150°K. These results were interpreted as follows: the crystal is composed of the oxonium ion OH3+ and the perchlorate ion ClO4−, the orientation of the oxonium ion being well fixed at lower temperatures. At high temperatures, above the transition point at 150°K, however, the oxonium ion begins to rotate around the centre of mass, resulting the narrowing of the absorption line. H–H distance in the oxonium ion was estimated to be 1.6∼1.7 Å, in good accord with the expected value from our knowledge about, the structure of the water molecule.
