Line sharpening effect due to PCI in Ar LMM Auger spectra: experimental and theoretical results

High-resolution argon LMM Auger spectra excited by electrons at two different excess energies (2750 and 30 eV) above the L3 level in Ar are presented. Due to post-collision interaction (PCI) the low-energy excited spectrum reveals a line sharpening effect of the low-energy sides of the peaks which are sharper than the corresponding Lorentzian. An extra structure at the high-energy side of the L2M2,3M2,3 (1D2) peak and an edge at 209 eV are observed. These are interpreted to be caused by electron shake down from the electron continuum to ionic Rydberg states. A new semiclassical theory for PCI in photoexcited Auger spectra is outlined. The theory leads to simple analytical expressions which reproduce the experimental Auger line shapes both at low and at high excess energies.

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