The Microwave Absorption Spectrum of Oxygen

Measurements of the absorption of 5-mm radiation in oxygen gas have been made. The experimentally observed magnitude and shape of the absorption may be satisfactorily compared with the theoretical curves of Van Vleck for an assumed line breadth $\Delta \nu =0.015\mathrm{} \mathrm{to} 0.02$ ${\mathrm{cm}}^{-1\mathrm{}}$. Observations of the absorption in mixtures of oxygen and nitrogen indicate a disparity of ${\mathrm{O}}_2$ and ${\mathrm{N}}_2$ collision cross sections. It is suggested that nitrogen causes an anomalous narrowing of the oxygen absorption line breadth.