Time-resolved radiation chemistry: dynamics of electron attachment to uracil following UV excitation of iodide-uracil complexes

Electron attachment to uracil was investigated by applying time-resolved photoelectron imaging to iodide-uracil (I(-)U) complexes. In these studies, an ultraviolet pump pulse initiated charge transfer from the iodide to the uracil, and the resulting dynamics of the uracil temporary negative ion were...

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Bibliographic Details
Published in:The Journal of chemical physics 2014-12, Vol.141 (22), p.224310-224310
Main Authors: King, Sarah B, Yandell, Margaret A, Stephansen, Anne B, Neumark, Daniel M
Format: Article
Language:English
Subjects:
ANIONS
ATOMIC AND MOLECULAR PHYSICS
Charge transfer
DIPOLES
Electron attachment
Electrons
ENERGY DEPENDENCE
EXCITATION
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
IODIDES
Iodides - chemistry
IODINE IONS
Ions
Models, Molecular
Negative ions
Organic chemistry
Photoelectron Spectroscopy
Physics
PULSE RISE TIME
PULSES
Radiation chemistry
Time dependence
TIME RESOLUTION
Ultraviolet Rays
ULTRAVIOLET SPECTRA
Uracil
Uracil - chemistry
URACILS
URANIUM COMPLEXES
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Summary:Electron attachment to uracil was investigated by applying time-resolved photoelectron imaging to iodide-uracil (I(-)U) complexes. In these studies, an ultraviolet pump pulse initiated charge transfer from the iodide to the uracil, and the resulting dynamics of the uracil temporary negative ion were probed. Five different excitation energies were used, 4.00 eV, 4.07 eV, 4.14 eV, 4.21 eV, and 4.66 eV. At the four lowest excitation energies, which lie near the vertical detachment energy of the I(-)U complex (4.11 eV), signatures of both the dipole bound (DB) as well as the valence bound (VB) anion of uracil were observed. In contrast, only the VB anion was observed at 4.66 eV, in agreement with previous experiments in this higher energy range. The early-time dynamics of both states were highly excitation energy dependent. The rise time of the DB anion signal was ∼250 fs at 4.00 eV and 4.07 eV, ∼120 fs at 4.14 eV and cross-correlation limited at 4.21 eV. The VB anion rise time also changed with excitation energy, ranging from 200 to 300 fs for excitation energies 4.00-4.21 eV, to a cross-correlation limited time at 4.66 eV. The results suggest that the DB state acts as a "doorway" state to the VB anion at 4.00-4.21 eV, while direct attachment to the VB anion occurs at 4.66 eV.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4903197