Far-Infrared Absorption in Solid Alpha Oxygen

Abstract

The far-infrared absorption spectrum of crystalline alpha oxygen ($\ensuremath{\alpha}\ensuremath{-}{\mathrm{O}}_{2}$) has been measured in annealed samples up to 20 mm thick. The prominent feature of the spectrum is a temperature-dependent absorption near 27 ${\mathrm{cm}}^{\ensuremath{-}1}$ which appears to be an anti-ferromagnetic resonance mode, the first such collective excitation to be observed in a molecular solid.