Research Interest/Area of Expertise
Photochemistry, ultrafast molecular dynamics, high harmonic generation and attosecond spectroscopy.
Professor Wen Li's research interests lie in developing and applying novel probes to study reaction dynamics at their most detailed level. The goal of our research is to understand, predict and eventually control a chemical reaction in the most effective way. The probes include strong field ionization and ultrashort electron and photon pulses produced from high order harmonic generation (HHG). HHG itself is also a strong field process that can be described semi-classically using a 3-step model: 1. ionization of a bound electron from an atom by a strong laser field; 2. propagation and acceleration of the electron in the laser field; 3. recombination of the electron with the ion core to emit high energy photons. Both the 'recombining' electron and the emitted photon can be used to probe chemical dynamics. Due to the intrinsic ultrafast property of HHG, the pulse duration of the photon and electron can be as short as a few tens of attoseconds (10-18s). These fast pulses enable us for the first time to directly probe the attosecond dynamics of the electrons, which play a dominant role in reactions relevant to physics, chemistry and biology.
Three main projects in Li lab are:
High harmonic generation (HHG) probes of molecular dynamics. Using the coherent recombining electrons in the process of HHG, one can monitor ultrafast nuclear and electronic dynamics. An example of this research direction was recently highlighted in a Science research article. We plan to pursue this study further by looking into the electronic dynamics of ions while the electron is away in the continuum.
Production and characterization of intense attosecond pulse trains (APTs) with pulse durations as short as 150 attoseconds
Probing attosecond electronic dynamics with APTs using two-photon attosecond spectroscopy. The systems of interest include correlated double ionization, charge transfer in polyatomics and photoionization induced electron relaxation.
These studies should reveal many details of the electron dynamics and provide an experimental tool capable of controlling electronic dynamics at the attosecond level. The experimental results also provide benchmarks for theoretical methods dealing with multi-electron and multi-dimension problems.
Education – Degrees, Licenses, Certifications
- B.S., Peking University (China), 2000
- Ph. D., Stony Brook University, 2006
- Research Associate, JILA, University of Colorado/NIST, 2006-2009
T. N. Herath, Y. Lu, S. K. Lee and W. Li*, "Strong field ionization depends on the sign of the magnetic quantum number", Phys. Rev. Lett. 2012, 109, 043004.
S. K. Lee, Y. F. Lin, L. Yan, W. Li*, "Laser-induced low-energy electron diffraction in aligned molecules", J. Phys. Chem. A, 2012, 116, 1950.
W. Li*, A. A. J-B, C. W. Hogle, V. Sharma, X. B. Zhou, H. C. Kapteyn and M. M. Murnane, "Visualizing electron rearrangement during the transition from a molecule to atoms", Proc. Natl. Acad. Sci. U.S.A, 2010, 107, 20219.
W. Li*, X.B. Zhou, S. Patchkovskii, R. Lock, A. Stolow, H. C. Kapteyn and M. M. Murnane, "Time-resolved dynamics in N2O4 probed with high harmonic generation", Science 2008, 322, 1207.
I. Thomann, R. Lock, V. Sharma, E.Gagnon, S. Pratt, H.C. Kapteyn, M. M. Murnane and W. Li*, "Direct measurement of the angular dependence of the single-photon ionization of aligned N2 and CO2", J. Phys. Chem. A. 2008, 112, 9382.
W. Li, R. R. Lucchese, A. Doyuran, Z. Wu, H. Loos, G. E. Hall, A. G. Suits, "Superexcited state dynamics probed with an Extreme-Ultraviolet Free Electron Laser," Phys. Rev. Lett. 2004, 92, 83002.
An artistic illustration of HHG probing of vibration/electronic dynamics in N2O4 (the cover of Science). Vibrating molecules of N2O4 emit a bright burst of X-rays when their N-N bond is extended (peak), but only a few X-rays when this bond is compressed (valley). (Left) Electron cloud structures (orbitals) when the N-N bond is compressed. (Right) Orbitals when this bond is stretched.
CHM 5550 Physical Chemistry Laboratory, 2 Credit hours W2016