Research in the Liu Group consists of spectroscopic studies on gas-phase molecules and condensed-phase materials in both frequency domain (using high-resolution laser systems) and time domain (using ultrafast laser systems). Our high-resolution studies center around the spectroscopic detection and characterization of reactive chemical intermediates, e.g., free radicals and molecules in excited electronic states. These studies lead to a detailed understanding of molecular structures and dynamics, and the nature of chemical bonding. Unambiguous identification and analysis of the experimentally obtained spectra is a prerequisite to subsequent work on the chemical reactions that involve these intermediates. We are particularly interested in molecular species with Jahn-Teller effect and pseudo-Jahn-Teller effect, vibronic (vibrational-electronic) interactions that cause spontaneous distortion of the symmetry of polyatomic molecules. Quantum chemistry calculations are used to help understand these molecules.
The goal of the ultrafast spectroscopy study in the Liu Group, which is carried out in the Ultrafast Laser Facility in the Conn Center for Renewable Energy Research, is to contribute to the advancement of renewable energy science and technology through basic spectroscopic studies. Currently, our research efforts are focused on the characterization of solar cell materials and understanding the fundamental dynamical processes in the materials and their interfaces, which are essential to their functions and applications.