High-Resolution Molecular Spectroscopy Group

Research Interests

Macroscopic properties of matter arise from interactions among the constituent molecules. High-resolution spectroscopic studies of small molecular aggregates provide valuable insights into these intermolecular interactions and the underlying molecular dynamics. Our group focuses on investigating small molecular aggregates to understand bulk phenomena, such as chemical reactions, crystallization, and solvation, from a molecular perspective. We are also interested in elucidating the origin of molecular species often found on comets and asteroids.

To pursue these goals, we have developed a Helium NanoDroplets Isolation Spectrometer in our lab at IIT Kanpur (HeNDI-IITK). This happens to be India's first and only HeNDI spectrometer and is among the very few of its kind worldwide.

Helium nanodroplets are clusters of a few thousand to tens of thousands of helium atoms, formed by expanding high-purity helium gas (20–60 bar) through a precooled nozzle (10–20 K) with a diameter of 5 μm. The resulting nanodroplets have an equilibrium temperature of 0.37 K and are superfluid. These droplets provide an ideal medium for isolating individual molecules and forming molecular aggregates. The isolated molecules can rotate and vibrate almost freely, resulting in molecular spectra that closely resemble their gas-phase spectra, with vibrational bands typically appearing within 2 cm⁻¹ of the gas-phase spectra.

Moreover, helium nanodroplets enable the study of chemical reactions at the microscopic level at 0.37 K. Such studies are crucial for understanding chemical processes in cold interstellar environments, where molecules have very little thermal energy.

Our spectrometer is equipped with a quadrupole mass spectrometer (m/z 2-510 u) and a high-resolution infrared laser source, which gives access to the spectral range of ~2500–4500 cm⁻¹ with a resolution of ~0.0001 cm⁻¹.

In addition to experimental work, we perform electronic structure calculations to complement and interpret our experimental findings.