Variations of the infrared spectra with the nature and structure of the rare earth metal halides

Abstract

The i.r. absorption spectra for the halides of La, Nd, Sm, Eu, Gd, Er, and Yb have been measured over the frequency range 4000-200 cm-1. Frequencies for the anhydrous rare-earth metal halides except the fluorides and lanthanum trichloride are reported for the first time. Some indications of a dependency of the i.r. spectra on the structure of the halides are pointed out. Two of the halides exhibited a characteristic band pattern: 350, 275 and 215 cm-1 for fluorides; 360, 280 and 210 cm-1 for chlorides. These bands varied only slightly with the nature of the rare-earth metal. The characteristic bands due to H2O are observed in most of the halides. Spectra were also measured for the dihalides of Eu(II). The fluorides could be obtained in the absolutely anhydrous state. However the other halides, although yielding analytical results which indicated 99·8 per cent purity, always exhibited i.r. spectra containing water bands. In addition to the familiar water bands at 1600 cm-1 and in the region 3600-3000 cm-1, two bands commonly occurred at 1400 and in the region 1150-1000 cm-1. Such bands are characteristic of D2O and also have been cited as evidence for polywater. © 1972.