Vibrational spectra of solid fluorine

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Abstract
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.