Pressure-induced absorption of microwave radiation by the oxygen molecule

Abstract

It has been known that microwave absorptions at 9, 23 and 60 GHz by high pressure oxygen gas are considerably greater than expected by conventional theory, except at 68.7 GHz. A reasonable explanation is the pressure-induced absorption, which enhances the well established magnetic dipole absorption at the 60 GHz region. A total of 4.3 p db/km ( p in atmosphere) of peak intensity is proposed to be due to the pressure-induced absorption in the 60 GHz region, compared to 145 db/km due to magnetic dipole absorption.