Infrared Spectra of Solid α- and β-Oxygen

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 C2h in a space group of C2h1. None of the spectra, including those of isotopic mixtures, suggest the presence of O4 molecules.