title: Electron accommodation dynamics in the DNA base thymine.
abstract: The dynamics of electron attachment to the DNA base thymine are investigated using femtosecond time-resolved photoelectron imaging of the gas phase iodide-thymine (I(-)T) complex. An ultraviolet pump pulse ejects an electron from the iodide and prepares an iodine-thymine temporary negative ion that is photodetached with a near-IR probe pulse. The resulting photoelectrons are analyzed with velocity-map imaging. At excitation energies ranging from -120 meV to +90 meV with respect to the vertical detachment energy (VDE) of 4.05 eV for I(-)T, both the dipole-bound and valence-bound negative ions of thymine are observed. A slightly longer rise time for the valence-bound state than the dipole-bound state suggests that some of the dipole-bound anions convert to valence-bound species. No evidence is seen for a dipole-bound anion of thymine at higher excitation energies, in the range of 0.6 eV above the I(-)T VDE, which suggests that if the dipole-bound anion acts as a "doorway" to the valence-bound anion, it only does so at excitation energies near the VDE of the complex.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: King
authors.affiliation: Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 København Ø, Denmark.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Stephansen
authors.affiliation: Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yokoi
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Yandell
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Alice
authors.initials: A
authors.lastname: Kunin
authors.affiliation: Department of Chemistry, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takayanagi
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Neumark
mesh_terms: D000838:Anions / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D004583:Electrons; D005740:Gases / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013941:Thymine / Q000737:chemistry*; D014498:Uracil / Q000737:chemistry
chemical_list: D000838:Anions; D005740:Gases; D000644:Quaternary Ammonium Compounds; C008076:3-(3-hydroxyphenyl)propyltrimethylammonium; D014498:Uracil; D004247:DNA; D013941:Thymine