Line positions and strengths of magnetic dipole transitions of molecular oxygen from stratospheric emission spectra

Submillimeter emission spectra of the low stratosphere (24.5 km) between 30 and 110 cm^-1 have been used to determine line positions and strengths for many of the lines originating in magnetic dipole transitions of the homonuclear molecule O₂. Observed line positions are shown to be in excellent agreement with recently derived theoretical values. Line strengths for these lines, many of which have never been measured in the laboratory, have also been obtained from these spectra. Measurements were made by utilizing the equivalent blackbody envelope defined by the peaks of heavily saturated H₂O lines throughout the spectrum to determine equivalent widths from the O₂ lines. The resulting line strengths are found to be significantly higher than values calculated on the basis of recent theoretical work and, for those lines for which a comparison is possible, higher than previously obtained laboratory determinations. This general feature of the present data is vital not only for the establishment of basic molecular parameters for O₂, but also for the application of recent methods for H₂O and O₃ stratospheric concentration determination in which O₂ lines are used as an internal calibration of the balloon-borne instrumentation.