https://doi.org/10.1140/epjd/e2002-00164-5
On the mechanism of nonradiative decay of DNA bases: ab initio and TDDFT results for the excited states of 9H-adenine
1
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 wolfgang.domcke@ch.tum.de
Received:
7
May
2002
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
