Anion formation moderated by post-collision interaction following core-level photoexcitation of CO

The photon-energy dependence of the oxygen-anion (O-) yield has been measured following photoexcitation of CO just above both the C and O K-shell ionization thresholds. The observed exponentially decaying yields above both edges are attributed to a post-collision interaction (PCI) between the emitted photoelectron and the CO molecule. Using a modified semi-classical atomic model, the near-threshold spectra can be reproduced if an energy shift is included. The shift in photon energy above the C K edge is greater than above the O K edge. The difference is attributed to a site-dependent PCI effect related to the polarity of the valence orbitals of the CO molecule. (author). Letter-to-the-editor