Time-resolved radiation chemistry: femtosecond photoelectron spectroscopy of electron attachment and photodissociation dynamics in iodide-nucleobase clusters

Iodide-nucleobase (I-center dot N) clusters studied by time-resolved photoelectron spectroscopy (TRPES) are an opportune model system for examining radiative damage of DNA induced by low-energy electrons. By initiating charge transfer from iodide to the nucleobase and following the dynamics of the resulting transient negative ions (TNIs) with femtosecond time resolution, TRPES provides a novel window into the chemistry triggered by the attachment of low-energy electrons to nucleobases. In this Perspective, we examine and compare the dynamics of electron attachment, autodetachment, and photodissociation in a variety of I-center dot N clusters, including iodide-uracil (I-center dot U), iodide-thymine (I-center dot T), iodide-uracil-water (I-center dot U center dot H2O), and iodide-adenine (I-center dot A), to develop a more unified representation of our understanding of nucleobase TNIs. The experiments probe whether dipole-bound or valence-bound TNIs are formed initially and the subsequent time evolution of these species. We also provide an outlook for forthcoming applications of TRPES to larger iodide-containing complexes to enable the further investigation of microhydration dynamics in nucleobases, as well as electron attachment and photodissociation in more complex nucleic acid constituents.