High-Resolution Molecular Spectroscopy Group

Research Interests

Macroscopic properties of matter are a manifestation of interactions among the constituting molecules. High-resolution spectroscopic studies on small molecular aggregates provide a means to explore various intermolecular interactions and molecular dynamics. Our group focuses on studying small molecular aggregates and understanding bulk phenomena, such as chemical reactions, crystallization, and solvation from a molecular point of view. We are highly interested in understanding the origin of molecular species found on comets and asteroids. For this purpose, we have built India's first helium nanodroplet spectrometer, which is among the very few of its kind worldwide. 

The helium nanodroplets are clusters of several thousand helium atoms, formed by expanding pressurised (20-60 bar) ultra-pure helium gas through a precooled nozzle (10-20 kelvin) of 5 μm diameter. The helium nanodroplets have an equilibrium temperature of 0.37 kelvin and are superfluid. These nanodroplets have proven to be an ideal medium to isolate individual molecules and form molecular aggregates. Molecules can rotate and vibrate almost freely inside the nanodroplets, thus observed molecular spectra are close to gas-phase spectra (vibrational bands are observed within 2 cm-1 of the gas-phase spectra). Moreover, helium nanodroplets facilitate the studies of chemical reactions at the microscopic level at 0.37 kelvin temperature. Studies of chemical reactions among cold molecules are important to understand the chemical processes that occur in interstellar space, where there is hardly any thermal energy available! 

The spectrometer is coupled to a high-resolution infrared laser source, which provides access to a spectral range of ~2550-4500 cm-1 with a resolution of ~0.0001 cm-1.

We also perform electronic structure calculations to complement our experimental findings.