Tarun Kumar Roy - Research Experience

Chemistry of Complex Environmental Interfaces of Aqueous Microdroplets and Atmospheric Aerosol

This research focuses on the chemistry of complex environmental interfaces, particularly aqueous microdroplets, and atmospheric aerosols. I am utilizing micro-spectroscopy techniques, including Raman and optical-photothermal infrared (O-PTIR) spectroscopy, to investigate aqueous or aerosol microdroplets and their interfacial processes. A key aspect of this work is studying the kinetics and mechanisms of complex chemical reactions at the air-water interface of aqueous microdroplets. These efforts aim to unravel interfacial reaction complexities and highlight the crucial role of microdroplet physicochemical properties.

Spectroscopy and Unimolecular Decay Dynamics of Reaction Intermediates

This research focused on characterizing jet-cooled, atmospherically relevant reaction intermediates, including carbon-centered •QOOH radicals and Criegee intermediates. We used various action spectroscopic techniques, such as time-resolved IR pump-UV probe spectroscopy and IR-VUV ion dip spectroscopy, to obtain infrared fingerprints and investigate the time- and energy-resolved unimolecular dissociation dynamics of these intermediates. We were able to probe targeted regions of the potential energy surface in complex, multi-step atmospheric reactions, enabling a detailed study of specific elementary steps. Additionally, using electronic spectroscopy, we characterized the largest stabilized Criegee intermediate under gas-phase conditions to date.

Helium Droplets IR Spectroscopy

Helium nanodroplets provide a unique environment for stepwise aggregation of molecular clusters and chemical reactions under isolated and ultracold conditions. This technique provides critical molecular-level insights into these processes, advancing our understanding of the structure and dynamics of embedded molecules at the ultracold temperature of helium droplets (0.37K). Through high-resolution infrared spectroscopy, microsolvation framework of prototype aromatic molecules are studied. Additionally, we demonstrated that the molecular aggregation process of polar molecules at sub-Kelvin temperatures can be precisely manipulated by utilizing the internal electric field generated by a single molecular dipole.