Unified model for the ultrafast decay of pyrimidine nucleobases.
Ultrafast decay processes detected after absorption of UV radiation in gas-phase pyrimidine nucleobases uracil, thymine, and cytosine are ascribed to the barrierless character of the pathway along the low-lying 1(pipi*) hypersurface connecting the Franck-Condon region with an out-of-plane distorted ethene-like conical intersection with the ground state. Longer lifetime decays and low quantum yield emission are on the other hand related to the presence of a 1(pipi*) state planar minimum on the S1 surface and the barriers to access other conical intersections. A unified model for the three systems is established on the basis of accurate multiconfigurational CASPT2 calculations, whereas the effect of the different levels of theory on the results is carefully analyzed.
Merchán
Manuela
M
Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071 Valencia, Spain.
González-Luque
Remedios
R
Climent
Teresa
T
Serrano-Andrés
Luis
L
Rodríguez
Elena
E
Reguero
Mar
M
Peláez
Daniel
D
D008956:Models, Chemical; D011741:Pyrimidine Nucleosides / Q000737:chemistry*
D011741:Pyrimidine Nucleosides