Double vacancies in the core of benzene

Because of the six equivalent carbon atoms in benzene, there is only one type of single core vacancy, but four different types of double core vacancies. The binding energies of single and double core vacancies are calculated and analyzed. Particular attention is paid thereby to reveal the relation between the single and double hole states. The π and σ electrons are found to contribute differently to the different types of double vacancies. It is generally stressed that double core ionization probes the bonding properties much more sensitively than single core ionization.