Paper Title
Mechanism of Photo Dissociation of Guanine through the Repulsive 1πσ* State: A CC2 Study

Abstract
The irradiation of saturated water solution of guanine with UV light showed insignificant changes in the absorption spectrum of the compound, which should be a consequence form the high photostability of the compound. The last fact was proved by the studied mechanisms of H-detachment of the Namino-H and O-H bonds of three tautomers: oxo-amino, hydroxy-amino, and hydroxy-imino. They were studied at the CC2/aug-cc-pVDZ level of theory. It was found that the driven state of each mechanism is the repulsive 1πσ* excited state whose reaction profiles lead to crossing points with the S0 energy curves. Keyword - CC2 Calculations, Excited States, Guanine, Reaction Paths.