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Resume The laser-Raman spectrum of a crystal of monoclinic β sulfur has been recorded at various temperatures above and under the transition point. The frequencies of the internal modes are close to the internal frequencies of α sulfur. The external modes show a behaviour typical of disordered crystals with a progressive ordering of the molecules when the temperature is lowered.

The vibrational spectra of single crystals of cesium triiodide and rubidium triiodide have been recorded at 120 and 40°K. From polarisation measurements, bands can be resigned by taking into account the factor group effect. Linear and slightly angular configurations of the I 3 − ion are discussed.

The low-temperature laser- Raman and infrared absorption spectra of an oriented single crystal of orthorhombic sulfur have been recorded. The assignment of the ν 1 , ν 5 and ν 7 modes (all at about 470 cm −1 ) is made; the frequency of the ν 3 mode, inactive in the molecule, but active in the crystal, is confirmed. The presence of only one b 1 u band of low frequency leads to the assignment of 30 and 45 cm −1 for the librations. Thus, translations are in the 50–70 cm −1 range.

Resume The vibrational spectra of 31 crystalline hexachloro and hexabromo-metallates have been recorded. The calculation of force constants has been carried out from a modified Urey-Bradley force field, including the effect of cations on the internal vibrations of the anion. The relation between the degree of covalency of the metal-halogen bond and the stretching force constant is discussed.

Resume The infrared spectra of some alkaline hexahalometal complexes have been recorded in the region 400–20 cm −1 , as crystalline powders.