Lifetime interference effect on the angular distribution of the Auger electron emission following resonant Auger decay from $2p \to 4s$ photoexcited Ar

A strong alternation of Auger electron angular distributions is observed for the second-step Auger emission of Ar following 2p3/2to4s and 2p1/2to4s excitation. This effect, which gives rise not only to anisotropy suppression but also to the strong enhancement, is shown to originate from a coherent population of the Auger initial state due to the short decay time of the second-step Auger transition, the so-called lifetime interference effect