Mechanisms of spontaneous two-electron emission from core-excited states of molecular CO.

We demonstrate that the observation of slow electrons emitted in the decay of molecular core-excited states can be a sensitive probe of the double Auger processes, and that in combination with electron-electron coincidence spectroscopy, it can provide clear insight into the mechanisms involved. The present study identifies all cascade Auger paths from the C1s-to-Rydberg states in CO to final states of CO{sup 2+}. One pathway includes the first directly identified case of molecular level-to-level autoionization of a cation and shows remarkable selectivity for a specific final state.