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 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 that are found on comets and asteroids. For this purpose, we are building a helium nanodroplet isolation machine that will be coupled with a high-resolution infrared laser source.

The helium nanodroplets are clusters of several thousand helium atoms, formed by expanding pressurised (20-50 bar) ultra-pure helium gas through a precooled nozzle (7-20 kelvin) of 5 μm diameter. The helium nanodroplets have an equilibrium temperature of 0.37 kelvin and are superfluid in nature. 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 the interstellar space, where there is hardly any thermal energy available! We also use electronic structure calculations to complement our experimental findings.