Raman Studies of Molecular Motion in Condensed Oxygen

Raman scattering has been observed from both the external and internal motions of the molecules in each of the four condensed phases of oxygen. The stretching vibration gives rise to a sharp band at 1552_.5 cm⁻¹ in each phase. Weak wings occur at the base of this band in the $\gamma$ and liquid phases. Librational lattice modes are observed at 44 and 79 cm⁻¹ in the $\alpha$ phase and at ∼ 50 cm⁻¹ in the $\beta$ phase. The intensities of these bands relative to that of the internal fundamental are in reasonable agreement with those expected from the oriented gas model. In γ‐ and liquid oxygen, the external motion gives rise to strong wings on the Rayleigh line. Estimates of the mean‐square torsional amplitude and the torque acting on the molecule have been made from the observed low‐frequency spectra, and indicate that the torsional motion is highly hindered in each phase. The root‐mean‐square torsional amplitude increases from an average of 9° in the $\alpha$ phase to 18° in the liquid.