Koopmans' Analysis of Chemical Hardness with Spectral-Like Resolution

Figure 1

The paradigmatic in silico spectra of the first three highest occupied and lowest unoccupied molecular orbitals illustrating the respective, successive, ionization and affinities energies as provided by Koopmans’ theorem. Note that KT implies ionization and affinity of one electron on successive levels and not of successive electrons on levels; see the marked occupied and virtual spin orbitals.