Shape-resonance-enhanced continuum–continuum coupling in photoionization of CO2

We have measured photoionization branching ratios and photoelectron asymmetry parameters for photoionization of CO2 leading to the first four electronic states of CO2+ over the photon energy range from 20 to 50 eV. The motivation for this work was the prediction by Lucchese [J. Chem. Phys. 92, 4203 (1990)] that the σu shape resonance in the (4σg)−1 C̃ 2Σg+ ionization channel would influence the photoionization dynamics in the other valence-shell continua through continuum–continuum channel interaction, with the main effect occurring in the (3σu)−1 B̃ 2Σu+ channel. Indeed, clear evidence for this phenomenon is observed in this channel, the most prominent indication being a broad, shallow minimum in the asymmetry parameter at ∼40 eV. Comparisons of the present results with theory and other measurements reflect good overall agreement and provide some guidance regarding the effectiveness of alternative approximations used in the theoretical calculations.