A photoelectron spectroscopy study of the valence shell photoionization dynamics of acetylene

Abstract The valence shell photoionization dynamics of acetylene have been studied in the photon energy range 13–140 eV using photoelectron spectroscopy and synchrotron radiation. Photoelectron angular distributions and branching ratios have been determined for the X 2 Π u , A 2 Σ g + , B 2 Σ u + and C 2 Σ g + single-hole ionic states and for two inner valence correlation states. An interpretation of the experimental results was carried out based upon previous theoretical predictions, and it appears that the photoionization dynamics are being strongly affected by shape resonance phenomena. The photoelectron asymmetry parameters associated with the A 2 Σ g + and the C 2 Σ g + ionic states provide the first experimental confirmation of the predicted σ u continuum shape resonance.