Far-Infrared Absorption in Solid Alpha Oxygen

Abstract

The far-infrared absorption spectrum of crystalline alpha oxygen ($\alpha -{\mathrm{O}}_2$) has been measured in annealed samples up to 20 mm thick. The prominent feature of the spectrum is a temperature-dependent absorption near 27 ${\mathrm{cm}}^{-1\mathrm{}}$ which appears to be an anti-ferromagnetic resonance mode, the first such collective excitation to be observed in a molecular solid.