Vibrationally resolved C and O 1s photoelectron spectra of carbon dioxide

Vibrationally resolved C 1s and O 1s photoelectron spectra of carbon dioxide have been measured with photon energies up to 500 and 700 eV, respectively. Vibrational branching ratios are nearly constant for the C 1s and O 1s photoelectron spectra recorded with the photon energies in the regions 400-500 and 600-700 eV, respectively, where neither shape resonance effect nor photoelectron recoil effect is significant. The information about the potential curves for the C 1s and O 1s ionized states are extracted from these spectra, using the Franck-Condon approximation. The experimental potential curves thus obtained are well reproduced by the present ab initio calculations based on the symmetry adapted cluster-configuration interaction (SAC-CI) method.