Single-photon double ionization of ozone: experiment and theory

The triatomic molecule ozone (O3) is of outmost physical and chemical importance in the atmospheres of our Earth and other planets. Beyond its environmental significance, a detailed understanding of the electronic structure and ionization dynamics of ozone is essential for modeling atmospheric, ionospheric, and astrochemical processes. In the present work, we substantially extend the experimental and theoretical characterization of ozone into the regime of valence double photoionization. Using He II-alpha, He II-beta, and higher-energy vacuum ultraviolet radiation in combination with a versatile multiple charged-particle correlation detection technique, we report the first single-photon valence double ionization electron spectrum of O3. To interpret the experimental observations, we mapped the lowest potential energy surfaces of O32+ employing post-Hartree-Fock multi-configurational-interaction methods, and computed with high accuracy the energetics of the relevant dissociation channels. Our results demonstrate that dissociative double ionization of ozone produces electronically excited O+ and O fragments in addition to the ground-state O2+ + O+ dissociation pathway, revealing richer fragmentation dynamics than hitherto recognized.