Excited and ionized states of ozone studied by the MEG (multi-exponentially generated)/EX (excited)-MEG method

The MEG (multi-exponentially generated)/EX (excited)-MEG method, which is a multi-reference version of the SAC (symmetry-adapted cluster)/SAC-CI (configuration interaction) method, has been applied to the valence excited and ionized states of ozone that has a quasi-degenerate bi-radical nature in its ground state. The MEG/EX-MEG result shows a remarkable improvement over the single-reference SAC/SAC-CI general-R one in both the correlation energy and the ionization potential. The present results were compared with the previous theoretical and experimental data. The theoretical ionization spectrum reproduced the experimental spectrum observed from outer- to inner-valence regions (∼28 eV). This is the first report that gives a theoretical interpretation up to a high-energy region.