ABSTRACT
Damage to the genome by UV light has fueled interest in excited
electronic states of DNA for over 50 years. DNA is also a fascinating
model system for understanding how two widespread supramole-
cular self-assembly motifs, π -π stacking and hydrogen bonding,
influence exciton dynamics in multichromophoric assemblies. The
importance of minimizing photochemical damage has endowed
DNA with remarkable photophysical properties that could inspire
new approaches to controlling exciton and charge transport in
nanomaterials. Although most excitations in single DNA bases decay
nonradiatively in hundreds of femtoseconds, much longer-lived
excited states are observed in femtosecond transient absorption
experiments on single-and double-stranded DNAs. Experiments on
single-stranded nucleic acids isolate effects due to base stacking.
Base stacking is shown to be of paramount importance for the
slow, nonradiative decay channels. This chapter provides a detailed
discussion of the femtosecond transient absorption technique with
emphasis on considerations relevant to studies of DNA excited-
state dynamics. A rate equation analysis of transient absorption
signal strengths is presented and used to reach conclusions about
excited states from experiments on single-stranded adenine homo-
oligonucleotides.
