Dissociation of acetonitrile molecules following resonant core excitations

Dissociation of acetonitrile molecules following resonant core excitations of carbon and nitrogen core electrons to the LUMO orbital was investigated using the electron-energy-resolved photoelectron–photoion coincidence (PEPICO) technique. The fragment ion mass spectra were recorded in coincidence with the resonant Auger electrons, emitted in the decay process of the core-excited states. Deuterated and 13C-substituted samples were used for fragment identification. The results showed the initial core hole localization to be of minor importance in determining the dissociation pattern of the molecular cation. The participator and spectator Auger transitions produce entirely different fragmentation patterns and the latter indicates that complex nuclear rearrangements take place. Using also the findings from the 13C labelling, it is suggested that the bending motion, induced in the core-excited state by the Renner–Teller effect, plays an important role in determining the most intense dissociation pathways of the spectator Auger final electronic states.