Electronic Configuration, Orbital Energies

The direct results from the SCF are the orbital energies and occupation numbers. This defines the electronic configuration: the occupation numbers and HOMO and LUMO energies for instance show whether or not the aufbau principle is satisfied in the final situation.

The energies of the Core Orbitals can be used to interpret for instance XPS (X-ray Photoelectron Spectroscopy) data: from Koopman's theorem these core orbital energies are an approximation to the core ionization energies. This neglects the effect of relaxation upon the ionization so that absolute energy values may not be very good; relative values, however, should be fair and can therefore be used to study (relative) chemical shifts.