Infrared Spectra of Solid α- and β-Oxygen

Abstract

The spectrum of solid α‐oxygen deposited at 15° or 20°K consists of a sharp absorption centered at 1549 cm⁻¹ (half‐width ∼4 cm⁻¹) and a more intense, broad absorption (half‐width ∼45 cm⁻¹) with well‐defined peaks at 1591 and 1617 cm⁻¹. Warming through the α—β phase transition (at 24°K) causes the broad band to become more diffuse. Recooling restores the low‐temperature spectrum and shows that the α—β transition is rapid and reversible. Slow deposition at 4°K gives an imperfect solid in which the sharp feature is very much intensified. The broad band is due to combinations involving translational lattice modes; the sharp feature is apparently the O₂ fundamental appearing because of lattice imperfections. The β‐oxygen spectrum indicates intermolecular force constants of 0.024 and 0.013 mdyn/Å and the α‐oxygen spectrum is consistent with a site symmetry of C_2h in a space group of C_2h¹. None of the spectra, including those of isotopic mixtures, suggest the presence of O₄ molecules.