Title: High-Resolution Molecular Spectroscopy on Multiple Potential Energy Surfaces
Time: 9:00, Thursday, May.25, 2023
Place: F310, School of Mechanical Engineering
Host: QI Fei,  Professor (Institute of Aerospace Propulsion)

Biography
Dr. Jinjun Liu is a Professor of Chemistry and Adjunct Professor of Physics at the University of Louisville (UofL) in Kentucky, U.S. (https://sites.google.com/site/uofllaserlabs/) As Spectroscopy Theme Leader of the Conn Center for Renewable Energy Research at UofL, he also runs an ultrafast laser spectroscopy lab. Dr. Liu is a recipient of the NSF CAREER Award (2015), the Flygare Award of the International Symposium on Molecular Spectroscopy (2017), and the Fundamental Physics Innovation Award of the American Physical Society (APS) and the Gordon and Betty Moore Foundation (2018). 

Abstract
High-resolution molecular spectroscopic investigations in our research lab center on the detection and characterization of reactive chemical intermediates, e.g., free radicals and molecules in excited electronic states. The spectroscopic methods employed include laser-induced fluorescence/dispersed fluorescence (LIF/DF) spectroscopy for alkoxy (RO·) radicals and cavity ring-down (CRD) spectroscopy for peroxy (ROO·) radicals. These two techniques are also used to study metal-containing molecules as candidates for direct laser cooling and the search for the origin of the matter-antimatter imbalance in the Universe. Recently, our group has started developing a novel cavity-enhanced two-photon double-resonance spectroscopy technique to investigate molecular “dark states”. We are particularly interested in molecular species with the Jahn-Teller (JT) effect and the pseudo-Jahn-Teller (pJT) effect, vibronic (vibrational-electronic) interactions that cause spontaneous distortion of the symmetry of polyatomic molecules in degenerate or nearly degenerate electronic states. High-level quantum chemistry calculation methods and effective-Hamiltonian spectroscopic models have been developed to help understand the geometry, energy level structure, and dynamics of molecules on multiple potential energy surfaces through spectroscopic analysis.