Experimental ionization energy correlation diagram

Figure 4. Experimental ionization energy correlation diagram of N2.

After this necessary excursion into the broad field of electron-electron interactions as described in diagrammatic language and by certain approximations, the effects of electron correlations beyond the RRPA approach can be summarized by using the following rules (neglecting the photoelectron s self-energy diagram) ISCI and FISCI must be taken explicitly into account, and the theoretical ionization threshold has to be adapted to the experimental value. 

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