Line-Breadths of the Microwave Spectrum of Oxygen

Abstract

Line-breadth parameters for oxygen have been determined with a Zeeman modulation spectrograph for fifteen microwave transitions occurring in the 5-mm wavelength region. Measured values lie in the range 0.0319 to 0.0516 ${\mathrm{cm}}^{-1\mathrm{}}$/atmos, with a population weighted mean of 0.0475 ${\mathrm{cm}}^{-1\mathrm{}}$/atmos. Investigation of the variation of the line-breadth parameter as a function of $K$, the rotational angular momentum quantum number, reveals greater line-breadth for the most populated states. This leads to an interpretation of the self-broadening collision process as a mechanism involving not only the quadrupole-quadrupole and polarizability interactions predicted theoretically, but also a rotational resonance interaction.