The carbon and oxygen K-edge NEXAFS spectra of CO<sup>+</sup>
Rafael C. Couto, Ludvig Kjellsson, Hans Ågren, Vincenzo Carravetta, S. L. Sörensen, Markus Kubin, Christine Bülow, Martin Timm, Vicente Zamudio‐Bayer, Bernd von Issendorff, J. Tobias Lau, Johan Söderström, Jan‐Erik Rubensson, Rebecka Lindblad
Abstract
We present and analyze high resolution near edge X-ray absorption fine structure (NEXAFS) spectra of CO+ at the carbon and oxygen K-edges. The spectra show a wealth of features that appear very differently at the two K-edges. The analysis of these features can be divided into three parts; (i) repopulation transition to the open shell orbital - here the C(1s) or O(1s) to 5σ transition, where the normal core hole state is reached from a different initial state and different interaction than in X-ray photoelectron spectroscopy; (ii) spin coupled split valence bands corresponding to C(1s) or O(1s) to π* transitions; (iii) remainder weak and long progressions towards the double ionization potentials containing a manifold of peaks. These parts, none of which has correspondence in NEXAFS spectra of neutral molecules, are dictated by the localization of the singly occupied 5σ orbital, adding a dimension of chemistry to the ionic NEXAFS technique.