Photo double detachment of CN−: Electronic decay from an inner-valence hole in molecular anions

The first measurements of inner-valence photodetachment from a molecular negative ion are presented. Experimental and theoretical studies of CN− photodetachment around the 2-electron threshold (25–90 eV) are reported. Included are measured absolute cross sections for CN+ production by photo double detachment of CN−, and for C+ and N+ fragments produced from the dissociation of the excited molecule. The measurements also reveal the signature of inner-valence autoionization, similar to the interatomic Coulombic decay (ICD) phenomenon. This work confirms the predicted effect, which should in general be present for molecular anions, even in very small molecules.