Raman and far infrared spectra of crystalline fluorine have been obtained in both solid phases. As expected for the disordered higher temperature form, only the Raman-active stretching fundamental is observed for β-F2. Near ∼ 20 °K α-F2 exhibits the following spectral features (in cm−1): Raman — ν(1 – 0) 985; ν(2 – 0) 1764; ν(libration) 44, 55, 77, (93?); infrared — ν(translation) 28, 42.5, 80. The predictions of a preliminary calculation of the optically active lattice frequencies for the low temperature phase are in poor agreement with the observed lattice frequencies, suggesting that an improved model will be required to help distinguish the correct α-F2 crystal structure. Solid fluorine more closely resembles oxygen that it does the other halogens. In particular, the intermolecular forces are extremely weak, as exemplified by the small shifts of the internal frequencies from their gas phase values, the absence of observable factor group splitting of the fundamental and the overtone, and the relatively low values of the external (lattice) frequencies.
NaIO 3 demonstrate that they are dependent on the volume of the crystalline unit cell. Except for small intensity contrbutions in some orientations which are probably due to depolarization effects in the birefringen" crystal, the polarizability activities of both the internal and external modes follow the expected symmetry selection rules.
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