Absolute oscillator strenghts for the valence-shell photoabsorption (2–200 eV) and the molecular and dissociative photoionization (11–80 eV) of nitrogen dioxide

Abstract

The valence-shell photoabsorption spectrum and absolute differential oscillator strengths (cross sections) of nitrogen dioxide have been measured at 1 eV FWHM resolution from the visible up to the soft X-ray energy region (2–200 eV) using dipole ( e, e) spectroscopy. The discrete spectral structures from 1.6 to 30 eV have also been studied at higher resolution (0.05 eV FWHM), and absolute oscillator strength values have been determined for the 2 B 1 ← 2 A 1 and 2BP 2 ← 2 A 1 systems as well as for the Rydberg states at higher energies. Comparisons have been made to previously reported absolute optical measurements in those limited energy regions where such data exist. The accuracy of the absolute oscillator strengths of nitrogen dioxide have been critically evaluated by comparison of the static electric—dipole polarizability of nitrogen dioxide derived from the present data using the S(−2) sum rule with those determined from dielectric constant measurements in the literature. In addition, dipole ( e, e + ion) coincidence spectroscopy has been used to obtain the photoion branching ratios, absolute photoionization efficiencies, and absolute partial differential oscillator strengths for the molecular and dissociative photoionization channels of nitrogen dioxide from the first ionization threshold up to 80 eV. Some qualitative deductions have been made concerning the dipole-induced breakdown pathways of nitrogen dioxide under UV, VUV, and soft X-ray radiation.