Temperature-dependent vibrational dynamics of molecules studied by time-resolved broadband terahertz spectroscopy

We report the development of a time-resolved broadband (100 GHz-12 THz) terahertz (THz) spectroscopy system using photoconductive antennas both to generate and detect ultrashort THz pulses. This system has been used to study the far-infrared vibrational modes of crystalline saccharides, and to understand the dynamics of both inter- and intra-molecular interactions. An anomalous temperature dependent absorption was observed, giving information about changes in the binding forces with temperature (300 K-4 K), the degree of anharmonicity of the vibrational energy levels, and the nature of the individual vibrational modes.