Electron accommodation dynamics in the DNA base thymine

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...

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Bibliographic Details
Published in:The Journal of chemical physics 2015-07, Vol.143 (2), p.024312-024312
Main Authors: King, Sarah B, Stephansen, Anne B, Yokoi, Yuki, Yandell, Margaret A, Kunin, Alice, Takayanagi, Toshiyuki, Neumark, Daniel M
Format: Article
Language:English
Subjects:
ANIONS
Anions - chemistry
BOUND STATE
Deoxyribonucleic acid
DIPOLES
DNA
DNA - chemistry
Ejection
ELECTRON ATTACHMENT
ELECTRONS
EV RANGE
EXCITATION
Gases - chemistry
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
IODIDES
IODINE
MEV RANGE
Negative ions
Photoelectron Spectroscopy
Photoelectrons
PULSES
Quaternary Ammonium Compounds - chemistry
THYMINE
Thymine - chemistry
TIME RESOLUTION
Uracil - chemistry
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Summary: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.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4923343