Chemical Dynamics Lab

The goal of our research is to follow fast and complex chemical dynamics under high (10^-6 Torr) or ultra high (10^-10 Torr) vacuum in picosecond (10^-12 second), femtosecond (10^-15 second) and attosecond (10^-18 second) time-scales.

Current Areas of Investigation Include

  1. Femtochemistry of catalysis and photocatalysis on metal nanoparticle surfaces under ultra high vacuum
  2. Development of Time-resolved photoelectron spectroscopy for chemical dynamics study in liquid under high vacuum
  3. Development of ultrafast X-ray pulses
  4. Attochemistry of non-covalently bonded clusters.
The Probes Include
  1. Temperature programmed desorption spectroscopy
  2. Femtosecond two-pulse correlation spectroscopy
  3. Time resolved photoelectron spectroscopy
  4. High order harmonic generation (HHG) spectroscopy
  5. Time-dependent quantum dynamics calculations
  6. Two temperature model-based simulation

Highlight of a few Recent Works:

  1. Development of Femtosecond X-ray Photoelectron Spectrometer
  2. Einstein (Nobel Prize 1921) discovered the law of photoelectric effect. One can build photoelectron spectrometer (Siegbahn received the Nobel Prize in 1981 for developing photoelectron spectroscopy) using the law of photoelectric effect to probe local chemical (electronic) environment of a species (gas, liquid or solid). During chemical reactions (such as photocatalysis, homogeneous catalysis, unimolecular decomposition), often local chemical environment changes in femtosecond to picosecond time scale. We are developing femtosecond X-ray photoelectron spectrometer to investigate chemical dynamics in gas, solid and liquid by monitoring the transient change of chemical environment (e.g., oxidation state of metal). A high pressure time-of-flight photoelectron spectrometer using magnetic bottle has been recently designed and built in our laboratory. We are currently evaluating the performance of this spectrometer. Design of the spectrometer is shown below. This spectrometer will be augmented by a home-built femtosecond X-ray beamline. Currently the beamline is also under development.

  3. Femtochemistry of Heterogeneous Catalysis at Nanoscale
  4. Heterogeneous catalysis is known for a long time and it is gaining increased attention due to dwindling fossil fuel resources. Many scientists have studied heterogeneous catalysis at the molecular (or fundamental) level. Let us take a few examples. Langmuir (received Nobel Prize in 1932) developed molecular understanding of surface catalysis. Hinshelwood (received Nobel Prize in 1956) developed molecular understanding of reaction kinetics on surface. Ertl (received Nobel Prize in 2007) developed understanding of surface catalytic reactions using low energy electron diffraction (LEED). Is there anything we do not understand today in gas phase heterogeneous catalysis?

    Real-life catalysts are made of supported nanoparticles. Femtochemistry (chemistry which occurs at the moment when bond breaks and forms) of catalysis on nanoparticle surfaces is mostly unexplored. We are currently exploring the Femtochemistry of CO desorption and oxidation reactions on Pd/Pt/Ru nanoparticle surfaces using two-pulse correlation spectroscopy under ultra-high vacuum conditions.

  5. Decomposition Dynamics of Rocket Fuels and energetic High Nitrogen Plasticizer
  6. Metal-contained energetic materials are used as Rocket fuel. Furthermore, high energy density materials are decomposed on catalyst bed to achieve forward thrust in rocket engine. We are exploring mechanistic and dynamical details of the decomposition of high energy materials in presence of metal particles (nanoparticles). Our recent work is shown below.

  7. Attochemistry of Noncovalent Bonded Clusters
  8. Charge migration is very fundamental event in chemistry. In a broader perspective, two mechanisms are found: (1) pure electronic mechanism which is driven only by electron-electron correlation and relaxation, and (2) coupled electron-nuclear mechanism which involves nuclear motion along with the charge migration. We are interested in the first mechanisms because this is mostly unexplored. In particular we are interested in exploring charge migration dynamics through non-hydrogen noncovalent bonds (such as halogen, chalcogen, pnicogen and tetrel bonds).

    Vertical ionization is a process which can be used to explore pure electronic aspect of charge migration in which nuclei do not take part. The procedure of quantum dynamics simulation of this hole migration dynamics at frozen nuclei include a few steps: the HOMO of the neutral is projected onto all stationary cationic molecular orbitals (obtained under unrestricted SCF-scheme) and then a time dependent phase factor (e-iEAt/h ) is introduced to the final equation of the hole orbital:

    One of our recent results is shown below

Representative Publications