The analysis of a photoelectron spectrum consists of the assignment of each band in the spectrum, to a particular electronic state of the molecular ion and, where this is meaningful, to ionisation from a particular orbital of the molecule. The first step is to ascertain, using a molecular orbital model, which orbitals are occupied and whether they are bonding, antibonding or nonbonding, degenerate or non-degenerate. But the exact order of the orbitals and ionisation bands in terms of energy is not reliably predicted by qualitative molecular orbital models; the main task in analysis is to determine this order.
In addition, it is helpful to compare a set of ionization potentials determined by the above equation with a set of calculated eigenvalues corresponding to each of the molecular orbitals. It is rarely expected that the comparison of the absolute energies will be very close but it is hoped that the ordering of the energies will be correct. The analysis of PE spectra is a complex process. To understand the PE spectra the effects of these following elements are to be studied: substituent, steric effect, lone pair orbitals, perfuoro effect, spin-orbit splitting and Jahn-Teller splitting, and vibrational structure.