Deactivation of UV-excited cytosine is investigated by non-adiabatic dynamics simulations, optimization of conical intersections, and determination of reaction paths. Quantum chemical calculations are performed up to the MR-CISD level. Dynamics simulations were performed at multiconfigurational level with the surface hopping method including four electronic states. The results show the activation of four distinct reaction pathways at two different subpicosecond time scales and involving three different conical intersections. Most trajectories relax to a minimum of the S1 state and deactivate with a time constant of 0.69 ps mainly through a semi-planar conical intersection along the nOπ* surface. A minor fraction deactivate along ππ* regions of the S1 surface. Sixteen percent of trajectories do not relax to the minimum and deactivate with a time constant of only 13 fs.
|Number of pages||11|
|Journal||Physical Chemistry Chemical Physics|
|State||Published - Mar 16 2011|