Observations of the Magnetic Dipole Rotation Spectrum of Oxygen

Abstract

PRELIMINARY work¹ gave a spectrum covering the wavelength range 1 mm to 300µ. of solar radiation passing through the atmosphere under conditions of low total water vapour. The expected absorption features resulting from the pure rotation lines of water vapour were recorded, but additional absorption features were present which could not be attributed to water and which in the earlier account¹ were tentatively ascribed to ozone, as this is the only other major atmospheric constituent with a permanent electric dipole moment. Subsequent experimental observations on ozone in the laboratory together with the analysis of E. K. Gora^2,3 showed that this explanation was not correct. About 3 years ago it was suggested that the absorption features at 14.2, 16.2 and 27.8 cm⁻¹ (Fig. 1) could be attributed to molecular oxygen which has a permanent magnetic dipole moment. Transitions had been predicted which provided a plausible explanation of the observed features, but no observations of the magnetic dipole rotation spectrum had been reported. The present work was undertaken to check at least qualitatively that this absorption was as predicted; this communication reports our preliminary results.