Emerging Leaders Program

Ellen Williams Distinguished Postdoctoral Fellowship
Research Topic: Time-Domain Nanoscience

Ultrafast optical and terahertz spectroscopy of molecules

Advisor(s):

Prof. Ki-Yong Kim

Research Description

The interaction of light with molecules is one of the fundamental phenomena in nature governing all organic and inorganic creatures. Upon irradiation of light at optical frequencies, molecules can scatter the incident photons non-elastically with a frequency shift determined by their electronic, vibrational, and rotational states. This non-elastic scattering can provide a wealth of information on the molecular energy states, but unfortunately, such phenomenon occurs extremely rarely, typically 1 out of 10 million events. In contrast, the molecular rotational and vibrational states can be directly probed at terahertz (THz) frequencies, at which small molecules rotate and biomolecules such as DNA and proteins resonantly vibrate. Such systems can be even actively controlled by high-energy, coherent THz pulses.

Here, we propose a three-track experimental program. In the first track (A), we will develop broadband THz time-domain spectroscopy to study the rotational and vibrational excitation of small polar molecules and biomolecules. In the second track (B), we will attempt to actively control molecular alignment and intermolecular vibrations with intense THz pulses. We will also develop femtosecond time-resolved optical/THz pump-probe spectroscopy for studying the dynamics of bimolecular conformation and molecular function. In the last track (C), we will investigate the possibility of producing a coherent ensemble of rotationally excited molecules for light amplification at broadband THz frequencies.