Femtosecond Time-Resolved Photoelectron Imaging of Small Biological Molecules

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. We are currently interested in recruiting group members to join us in this work.

Molecules studied:

Biomolecules

Solvent cluster anions

Information obtained:

Femtosecond dynamics of anion excited states, charge transfer and accomodation dynamics.

Project members:

Megan Asplund

Masafumi Koga

Jenny Wu

Recent publications:

♦ "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

♦ "Time-resolved photoelectron imaging of iodide-nitromethane (I^--CH₃NO₂) photodissociation dynamics" A. Kunin, W-L. Li, D. M. Neumark, Phys. Chem. Chem. Phys., 18, 33226 (2016). pdf

♦ "Photodissociation dynamics of the iodide-uracil (I-U) complex" W-L. Li, A. Kunin, E. Matthews, N. Yoshikawa, C. E. H. Dessent, D. M. Neumark, J. Chem. Phys. 145, 044319 (2016). pdf