THE ELECTRONIC ABSORPTION-SPECTRUM OF NH-3 IN THE VALENCE SHELL DISCRETE AND CONTINUUM REGIONS - ABSOLUTE OSCILLATOR-STRENGTHS FOR PHOTOABSORPTION (5-200 EV)

The electronic spectrum and the absolute photoabsorption oscillator strengths (cross sections) for the valence shell of NH3 have been measured using high- (0.048 eV fwhm) and low-resolution (almost-equal-to 1 eV fwhm) dipole (e, e) spectroscopy in the photon energy ranges 5.0-31 and 5.5-200 eV, respectively. The high-resolution data have been obtained at vibrational resolution and have been used to determine the integrated oscillator strengths of several vibronic transitions in the discrete absorption region below the first ionization potential. The oscillator strength data are compared with previously published absolute measurements obtained using direct optical techniques and electron impact spectroscopy. Criteria are discussed for estimating the corrections for Pauli-excluded transitions required for the normalization of relative photoabsorption spectra when using the partial Thomas-Reiche-Kuhn sum rule.