The photoabsorption cross section of O2 from 55–350 Å

The photoabsorption cross section of O2 was measured photoelectrically in the wavelength range 55–350 Å. The 250 MeV storage ring at the National Bureau of Standards provided the background continuum. The absolute accuracy of the measurements is ±3% between 55–140 and 170–300 Å and ±5% in the wavelength range 140–170 and 300–350 Å. The cross section decreased monotonically with increasing photon energy. No thresholds or new structure was observed in the total cross section.