On the intrinsic population of the lowest triplet state of thymine.
The population of the lowest triplet state of thymine after near-UV irradiation has been established, on the basis of CASPT2//CASSCF quantum chemical calculations, to take place via three distinct intersystem crossing mechanisms from the initially populated singlet bright 1pipi* state. Two singlet-triplet crossings have been found along the minimum-energy path for ultrafast decay of the singlet state at 4.8 and 4.0 eV, involving the lowest 3npi* and 3pipi* states, respectively. Large spin-orbit coupling elements predict efficient intersystem crossing processes in both cases. Another mechanism involving energy transfer from the lowest 1npi* state with much larger spin-orbit coupling terms can also be proposed. The wavelength dependence measured for the triplet quantum yield of pyrimidine nucleobases is explained by the location and accessibility of the singlet-triplet crossing regions.
Serrano-Pérez
Juan José
JJ
Instituto de Ciencia Molecular, Universitat de València, Apartado 22085, ES-46071, Valencia, Spain.
Gonzalez-Luque
Remedios
R
Merchan
Manuela
M
Serrano-Andrés
Luis
L
D008958:Models, Molecular; D008968:Molecular Conformation; D013941:Thymine / Q000737:chemistry*
D013941:Thymine