Nonlinear THz Spectroscopy of Molecular Liquids

Molecular dynamics in the condensed phase, including the restricted and diffusive rotational and translational motions, have decisive impact on the thermodynamic properties, chemical reactivity and biological functionality of molecular systems. To model these properties, microscopic insight on the origin of the collective and cooperative molecular motions and the strength of intermolecular interactions are required. In other words, the energy potential governing the intermolecular interactions needs to be determined experimentally. 

The following questions shape our current research program:  

1. How do the specific intermolecular interactions, such as hydrogen bonding, influence the molecular motions in the condensed phase?
2. How many molecules are involved to shape the dynamics of an intermolecular mode or process?
3. How a relaxation process starts and evolves in molecular liquids?
4. What is the mechanism of energy dissipation among intermolecular degrees of freedom?
5. What is the role of breaking and reforming of hydrogen bonds on the rotational dynamics of water?  
6. How confined molecular motion differs from that in the bulk? Can the encapsulated molecules such as H₂O@C₆₀ system, help answering this question?

To answer these questions, we use intense THz pulses, in resonance with rotational and/or translational molecular motions, to drive nonlinear effects in molecular systems. We also develop simple analytical models by which the initial understanding of such light-matter interaction processes can be obtain.