Knowledge Bank

Cross sections of oxygen at 300 K have been obtained from photoabsorption measurements at various pressures, from 50 to 760 torr, throughout the wavelength region 193-204 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The spectral features contributing to absorption in this region are the discrete lines of some Schumann-Runge bands and underlying dissociation continua consisting of the weak Herzberg continuum of $O2$ and a pressure dependent continuum attributed to the collision complex $O4$. Analysis of the pressure dependence of the total continuum cross section measured in window regions between discrete lines yields the Herzberg continuum cross section, for which our value is smaller than previous laboratory determinations in this region. Band oscillator strengths $f(0,0)=2.95\times 10-10$ and $f(1,0)=3.13\times 10-9$ of the (0,0) and (1,0) Schumann-Runge bands have been determined by direct numerical integration of the measured discrete cross section remaining after subtraction of the continua from the total cross section. This work is supported by the Chemical Manufacturers Association Agreement FC 82-412 with Harvard College.