Coster-Kronig decay of the Ar 2s hole observed by Auger-threshold photoelectron coincidence spectroscopy

The Coster-Kronig lines associated with Ar 2s decay have been resolved within the natural linewidth of the 2s hole for the first time. This was possible by a new spectroscopic technique, relying on resonance enhanced double photoionization. Auger-threshold photoelectron coincidence spectroscopy. Contrary to standard Auger spectroscopy, this technique can filter out weak components in Auger spectra corresponding to a well-defined inner-shell state and, furthermore, can achieve a resolution no longer limited by the lifetime of the inner-shell hole.