Journal of Physical Chemistry A, Vol.124, No.25, 5089-5097, 2020
Excited State Deactivation Mechanism in Protonated Uracil: New Insights from Theoretical Studies
We have conducted here a theoretical exploration, discussing the distinct excited state lifetimes reported experimentally for the two lowest lying protonated isomers of uracil. In this regard, the first- principal computational levels as well as the nonadiabatic surface hopping dynamics have been employed. It has been revealed that relaxation of the (1)pi pi* state of enol-enol form (EE+) to the ground is barrier-free via out-of-plane coordinates, resulting in an ultrashort S-1 lifetime of this species. For the second most stable isomer (EK+), however, a significant barrier predicted in the CASPT2 S-1 potential energy profile along the twisting coordinate has been proposed to explain the relevant long lifetime reported experimentally.