Experimental and theoretical investigation of the complete valence shell ionization spectra of CO₂and N₂O

The valence electron ionization spectra of CO₂, and N₂O are studied by dipole (e-2e) spectroscopy and 2ph-TDA many-body Green function calculations. Intense satellite structure in the (e-2e) spectra between ≈ 20 eV and ≈ 30 eV binding energy is assigned with the help of the calculations. While for CO₂, only satellite lines of ²Π_u symmetry appear with significant intensity, intense satellite lines of both ²Π and ² γ symmetry are found for N₂O in the 20-30 eV energy range. The theory predicts a complete breakdown of the molecular orbital picture of ionization to occur for the two innermost valence electrons of CO₂ and N₂O. The inner valence part of the ionization spectra of CO₂ and N₂0 is found to be considerably more complex than has hitherto been assumed. The experimental spectra confirm the main features of the theoretical results.