The electronic structure of the ozone molecule O3 has been studied with spectroscopy techniques and computations. The investigation was focused on O3 in a core-hole state. The electronic configuration and the nuclear dynamics have been found to be highly correlated.
This electron correlation is mapped out for the two chemically different sites in the molecule: the central and the terminal oxygen. The energy difference between the corresponding core orbitals is 4.58 eV, which allows for site-selective core ionization and core excitation.
The influence of the core-hole site on the electronic structure is substantial, which is shown with ion and electron spectroscopy data and ab-initio quantum chemical computations. Moreover, the induced nuclear motion differs considerably for the two core-hole sites.
One of the core-excited states is proven to be ultra-fast dissociative. An analysis of the data with a formalism for two-body dissociation disclosed the localized character of core excitation. The symmetry-equivalent terminal-oxygen core orbitals do have very little overlap, so that a delocalized model for the core excitation becomes inadequate.
Moreover, core-excitation opens up a decay channel to a valence-ionized state that has not been observed with photoionization. The reason for this state to have low cross section for photoionization is illuminated with a CASSCF computation of the electronic configuration. The configuration of the state was found to be very distinct from the ground state configuration.
Another effect of configuration-interaction was found in MRCI computations of the core- ionized states. Several local minima with distinct electronic configurations could be identified.