Single, double, and triple Auger decays from 1s shake-up states of the oxygen molecule

The single, double, and triple Auger decays from the 1s shake-up states of O₂ have been studied using a multi-electron coincidence method. Efficient populations of two-hole final states are observed in single Auger decays of the π-π^∗ shake-up states, which is understood as a characteristic property of the Auger transitions from shake-up states of an open-shell molecule. The O₂³⁺ populations formed by double Auger decays show similar profiles for both the O1s^-1 and shake-up states, which is due to the contributions from cascade double Auger processes. While the cascade contributions to the double Auger decays increase with the initial shake-up energy, the probability of direct double Auger processes remains unchanged between the O1s^-1 and shake-up states, which implies a weak influence of the excited electron on the double Auger emission that originates from the electron correlation effect.