Indirect processes, double photoionization

Its chief characteristic is that the excess energy of the photon above the double ionization threshold is shared as a continuous monotonic distribution between the two outgoing electrons. This direct double photoionization is contrasted with several indirect processes, of which by far the most important can be written... 

The prototypical indirect double photoionization process is the classical Auger effect, where the single-hole state created by ejection of an inner-shell electron exists for a significant time before ejection of a second electron. Alternatively, an intermediate singly charged state may exist as a multiply excited valence state or a Rydberg state, but whatever its nature, a lifetime of at least a few femtoseconds will normally allow the whole process to be considered as a sequence of two distinct steps. A sharp peak in the photoelectron spectrum and also, therefore, in... 

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