Influence of multielectron excitations on the O 1s photoionization in CO2

High-resolution O 1s photoelectron spectra of the CO2 molecule have been measured in the region of the resonant features above the O K edge. The cross sections and asymmetry parameters were determined for the vibrational components of the O 1s photoelectron line. The vibrational fine structure is completely dominated by the antisymmetric stretching mode, which arises due to vibronic coupling. The O 1s line is accompanied by a rich satellite structure. Auger electron spectra have been measured at the energies of the continuum resonances and used as an indirect probe for multielectron excitations. The shoulder on the low-energy side of the 4?u shape resonance is due to double excitations that decay via spectator processes.