Femtosecond Time-Resolved Photoelectron Spectroscopy of Molecular Anions

Femtosecond time-resolved photoelectron spectroscopy (TRPES) is a powerful technique to probe the ultrafast excited state dynamics ofmolecules.TRPES applied to gas-phase molecular anions and clusters is capable of probing not only excited state formation and relaxation but also electron accommodation dynamics upon injection of an excess electron into a solvent or molecule.We review the basics of TRPES as it applies to molecular anions and several applications including the study of electron solvation dynamics in clusters and excited state relaxation in several biomolecules. We then explore in detail the dynamics of electron attachment and photodissociation in iodide-nucleobase clusters studied by TRPES as a model system for examining radiative damage ofDNAinduced by low-energy electrons. By initiating charge transfer from iodide to the nucleobase and following the dynamics of the resulting transient negativeions with femtosecond time resolution, TRPES provides a novel window into the chemistry triggered by the attachment of low-energy electrons to nucleobases.