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Synopsis
The dynamics of the decay of excited biomolecule anions are monitored by femtosecond time-resolved photoelectron imaging (TRPEI) spectroscopy. Anion species are created by charge-transfer from an associated halide ion initiated by an ultraviolet pulse. The lifetime and decay dynamics of the anion species can then be monitored from their inception to their disappearance by photodetaching the excess electron with a second femtosecond pulse. Velocity map imaging detection permits interpretation of nearly 100% of detached electrons and the collection of both electron kinetic energy distributions, which provide information about how strongly the electron is associated with the initial anion species, and photoelectron angular distributions, which provide information about the orbitals from which the electron was detached.
The TRPEI technique has been applied to a wide variety of systems in our laboratory, but our current and future efforts focus on iodide-biomolecule clusters. With this technique, we are able to observe anion transformations and decay processes including autodetachment and dissociation in real time.
Molecules studied:
Biomolecules
Solvent cluster anions
Information obtained:
Femtosecond dynamics of anion excited states, charge transfer and accomodation dynamics.
Recent publications:
"Time-resolved photoelectron spectroscopy of iodide–4-thiouracil cluster: The ππ* state as a doorway for electron attachment" M. Asplund, M. Koga, Y. J. Wu, D. M. Neumark, J. Chem. Phys., 160, 054301 (2024). pdf
"Electron attachment dynamics following UV excitation of iodide-2-thiouracil complexes" M. Koga, M. Asplund, D. M. Neumark, J. Chem. Phys., 156, 244302 (2022). pdf
"Time-resolved dynamics in iodide-uracil-water clusters upon excitation of the nucleobase" A. Kunin, V. S. McGraw, K. G. Lunny, D. M. Neumark, J. Chem. Phys., 151, 154304 (2019). pdf
"Time-resolved radiation chemistry: Femtosecond photoelectron spectroscopy of electron attachment and photodissociation dynamics in iodide-nucleobase clusters" A. Kunin, D. M. Neumark, Phys. Chem. Chem. Phys., 21, 7239 (2019). pdf
"Dynamics of electron attachment and photodissociation in iodide-uracil-water clusters via time-resolved photoelectron imaging" A. Kunin, W-L. Li, D. M. Neumark, J. Chem. Phys. 149, 084301 (2018). pdf
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