Terahertz Spectroscopy of Biopolymers in Water: Absorption and Circular Dichroism

Biological polymers are expected to exhibit broad low frequency spectral features in the terahertz regime, corresponding to functionally relevant, global and sub-global collective modes with periods on the picosecond timescale. We have developed a broad band terahertz spectrometer suitable for studying these collective modes of biomolecules in their natural water environment. Radiation is provided by harmonic multipliers (up to 210 GHz) and the UCSB free-electron lasers (up to 4.8 THz). The spectrometer combines these sources with a cryogenic detector, a variable path length sample cell, and a circular polarizing interferometer. The spectrometer offers an opportunity to probe the terahertz dynamics of biopolymers in water by terahertz absorption, and terahertz circular dichroism spectroscopy.