Knowledge Bank

The continuum cross section of oxygen at 296-300 K has been measured with a resolution of 0.13 nm throughout the wavelength region 205-241 nm with oxygen pressures from 5 to 760 torr and optical lengths from 13.3 to 133 m. The three processes contributing to the observed cross section are absorption into two continua, viz., the Herzberg continuum of $O2$ and a pressure-dependent continuum involving two molecules of $O2$, and Rayleigh scattering. Extrapolation of the observed cross section to zero pressure yields the continuum cross section of $O2$, from which the calculated Rayleigh scattering is subtracted to give the Herzberg continuum absorption cross section of $O2$. Our previous Herzberg continuum cross $sections1$ obtained from studies at high resolution (0.0013 nm) between the Schumann-Runge absorption lines in the region 194-204 nm, are combined with the present results to give the Herzberg continuum cross section at 1 nm intervals throughout the region 195-241 nm. Comparison between different laboratory measurements and in situ stratospheric studies will also be presented. This work is supported by the Fluorocarbon Program Panel of the Chemical Manufacturers Association under Agreements FC 82-412 and FC 83-486 with Harvard College.