Electronic Structure and Core-Hole Dynamics of Ozone : Synchrotron-radiation based studies and ab-initio calculations

Abstract: 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.