Absolute dipole oscillator strengths for the photo-ionization and photoabsorption of COS (5–50 eV)

Abstract

Absolute dipole oscillator strengths (cross-sections) for photoabsorption and photoionization (total and partial) of COS have been derived from electron energy loss and (e, 2e) coincidence measurements in the energy range 5–50 eV. The oscillator strength distribution of COS is concentrated at lower energies in comparison to that observed for the valence isoelectronic molecules CO 2 and N 2O, a result which reflects the atomic sulfur contribution to the total oscillator strength. Consideration of the total photoabsorption and photoionization cross-sections indicates that Rydberg levels populated by absorption in the 12–19 eV region can decay by competing neutral processes (dissociation, fluorescence) and autoionization. Strong autoionization is supported by the unusually large partial oscillator strength of the X 2II(3π) −1 channel in the 12–16eV excitation range. Finally, binding energy spectra recorded at excitation energies above 20 eV exhibit extensive final-state structure.The many-body character of these states and their total (summed) intensity variation with energy have been examined.