High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge absorption bands of isotopic oxygen, 16O 18O, at 79 K

Abstract

Cross-sections of 16O 18O at 79 K have been obtained from photoabsorption measurements on mixtures of 16O 2, 18O 2 and 16O 18O at various pressures throughout the wavelength region 180.5–195.3 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines mm −1 grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross-sections of the 16O 18O Schumann-Runge bands (11, 0)-(3, 0) are independent of the instrumental width. The measured crosssections are presented graphically and are available at wavenumber intervals of ~0.1 cm −1 as numerical compilations stored on magnetic tape from the National Space Science Data Center, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. Band oscillator strengths of those bands have been determined by direct numerical integration of the measured absolute cross-sections and are in agreement with our theoretically calculated values.