THz spectroscopy on condensed phases; molecular crystals, proteins, and aqueous solutions

Abstract

The low-frequency region below several terahertz corresponds to intermolecular modes of complexes and intramolecular modes with a weaker potential force and/or larger reduced mass.
Intermolecular interactions such as hydrogen bonding, van der Waals forces and charge-transfer interactions play important roles in various chemical and biological processes. Moreover, the low-frequency spectra also reflect molecular dynamics on a time scale from picoseconds to femtoseconds. There has been dramatic progress in the generation and detection techniques of freely propagating THz radiation in the past two decades. THz radiation spectroscopy is an attractive method for studying dynamics in condensed phases with time scales of sub- picoseconds and picoseconds. We have widely applied this technique to investigate low-frequency dynamics of various kinds of condensed materials, including ionic liquids, solutions of non-polar solvents, proteins and polypeptides, and molecular crystals.