On the mechanism of nonradiative decay of DNA bases: ab initio and TDDFT results for the excited states of 9H-adenine
Institute of Physics, Polish Academy of Sciences, 02668 Warsaw, Poland
2 Institute of Physical and Theoretical Chemistry, Technical University of Munich, 85747 Garching, Germany
Corresponding author: a firstname.lastname@example.org
Published online: 13 September 2002
Minimum-energy reaction paths and corresponding potential-energy profiles have been computed for the lowest excited states of the amino form of 9H-adenine. Complete-active- space self-consistent-field (CASSCF) and density functional theory (DFT) methods have been employed. The potential-energy function of the lowest state, nominally a 3s Rydberg state, is found to be dissociative with respect to the stretching of the NH bond length of the azine group. The potential-energy function intersects not only those of the and excited states, but also that of the electronic ground state. The – and –S0 intersections are converted into conical intersections when the out-of-plane motion of the active hydrogen atom is taken into account. It is argued that the predissociation of the and states by the state and the conical intersection of the state with the S0 state provide the mechanism for the ultrafast radiationless deactivation of the excited singlet states of adenine.
PACS: 31.15.Ew – Density-functional theory / 31.25.Qm – Electron correlation calculations for polyatomic molecules / 31.50.Gh – Surface crossings, non-adiabatic couplings
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002