Photoemission of threshold electrons in the vicinity of the xenon 4d hole: Dynamics of Auger decay

Threshold electrons observed in the vicinity of the Xe 4d inner shell hole are shown to have three possible origins: double photoionization of valence electrons, release of 4d photoelectrons or Auger processes with the emission of two electrons. Coincidence spectra were taken between these threshold electrons and the associated fast ones. On the 4d → np resonances, they show that ejection of two Auger electrons is due to a two-step process and that simultaneous removal of two electrons is limited at most to the formation of excited Xe²⁺* states. Above the 4d threshold, coincidence lineshapes are distorted by post-collision interaction and reflect the decay dynamics of the 4d hole. An analysis within the eikonal approach reveals that the dominant process is decay of Xe⁺ (4d^-1) to Xe³⁺ through cascade emission of a threshold Auger electron followed by a fast Auger electron. A more refined analysis shows that the intermediate Xe²⁺* states must be short-lived (widths of more than 400 meV) and that double Auger decay i.e. simultaneous ejection of two electrons, can contribute as well.