X-ray emission–photoion coincidence spectroscopy of the CO2 molecule at the O 1s edge

Molecular dissociation following radiative decay of O 1s hole states in CO2 has been studied by detecting photoions in coincidence with undispersed soft X-ray emission. The production of ions after radiative decay is observed to increase from practically nothing at the O 1s → π∗ excitation to the appearance of CO 2 + , CO+, C+ and O+ ions when core-valence double excitations and O 1s shake-up transitions are induced. De-excitation pathways involving radiative decay from different core–hole states are discussed in order to interpret the results. A weak CO 2 2 + signal is attributed to the radiative Auger effect.