Embedded Files
1. Ultrafast Structural Dynamics of Complex Molecular Systems
1. Ultrafast Structural Dynamics of Complex Molecular Systems
Investigating how atoms and molecules interact via chemical bonds to form new chemical compounds is fundamental to understand Chemistry. Past discoveries have laid the foundation for many practical applications such as creating new medicines, developing green materials and designing electronic devices. The ability to “watch” chemical reactions with atomic scale spatial resolution and sub-femtosecond temporal resolution can revolutionize our understanding of chemical transformations. This is expected to lead to new chemical reactions created through the control and manipulation of atoms and electrons in molecules on ultrafast time scales. Novel beam sources like x-ray free electron lasers (XFELs) have unprecedented brilliance, time resolution and tunability, offering new opportunities for observing chemical processes and exploring fundamental molecular properties that were hidden in the past.
We are particularly interested in extending the current capabilities of ultrafast molecular diffraction to molecular systems of increasing complexity. We aim to address this complexity in two directions:
(1) Ultrafast molecular dynamics in complex environments (e.g., in solution)
(2) Quantum dynamics in molecules where quantum effect plays an important role (e.g., conical intersection dynamics or attosecond dynamics)
To achieve this, we perform ultrafast x-ray/electron scattering experiments in gas phase and liquid phase using Synchrotrons/XFELs at national labs, aiming to track ultrafast quantum motions of nuclei and electrons in molecules in both space and time.
Ultrafast x-ray (top) and electron (bottom) scattering set-up. The reaction of molecule is initiated with a laser pump pulse, and the time-evolving molecular structure is probed by scattering using X-ray/electron probe pulses with a variable time delay. The scattering signals are recorded with a pixelated detector.
The Advanced Photon Source at Argonne National Laboratory
Linac Coherent Light Source at Slac National Accelerator Laboratory
2. Ultrafast Molecular Spectroscopy
2. Ultrafast Molecular Spectroscopy
We conduct ultrafast molecular spectroscopy with our own table-top femtosecond laser systems and spectrometers. Ultrafast Spectroscopy and Scattering are complementary techniques. Scattering experiment is a direct probe of the molecular structure while Spectroscopy measures the energies of the molecule. Spectroscopic measurements thus can provide vital information about time-evolving electronic and vibrational states during chemical reaction dynamics.
3. Theoretical Spectroscopy
3. Theoretical Spectroscopy
We develop theoretical methods that can predict experimental signals accurately. Advanced theoretical tools for recovering desired molecular properties from measured data will be investigated. Molecular systems that are ideal for experiments will be suggested through quantum dynamical simulations.
We also design novel techniques that can observe new phenomena by manipulating attosecond electron dynamics, and develop new experimental concepts that can reveal chemical information unavailable otherwise.
We are developing vortex (twisted) x-ray diffraction as a promising imaging tool for unveiling molecular symmetry.
We proposed a new technique, vortex beam diffraction, that can directly image transient electronic coherences in molecules generated upon photoexcitation or near conical intersections.
Page updated
Report abuse