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Molecular and Organic Interactions

  • A. G. Davies
  • E. H. Linfield
Conference paper
Part of the NATO Science for Peace and Security Series book series

We review a selection of recent technological advances in terahertz frequency time-domain spectroscopy. We discuss the coherent generation of ultra-broadband terahertz radiation using a biased and asymmetrically excited low-temperature-grown GaAs photoconductive (PC) emitter. Using a backward collection method, terahertz radiation with frequency components over 30 THz can be collected, the highest observed for PC emitters. We outline two detection schemes, electro-optic (EO) detection using a ZnTe crystal, and PC-detection using a low-temperaturegrown GaAs PC receiver. The use of the PC receiver provides the timedomain spectroscopy system with a smooth spectral distribution between 0.3 and 7.5 THz, ideal for spectroscopic applications. We illustrate the technological developments with examples of transmission spectroscopy of polycrystalline organic materials. Specifically, we review measurements of the vibrational spectra of polycrystalline purine and adenine over the temperature range 4–290K. A number of well-resolved absorption peaks are observed, which are interpreted as originating from intermolecular vibrational modes mediated by hydrogen bonds. As the temperature is reduced, the observed absorption bands resolve into narrower peaks and some shift towards higher frequencies, which can be explained by the anharmonicity of the vibrational potentials. An empirical expression is given to describe this frequency shift.

Keywords

Vibrational Mode Organic Interaction Observe Absorption Band ZnTe Crystal Phonon Resonance 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer 2007

Authors and Affiliations

  • A. G. Davies
    • 1
  • E. H. Linfield
    • 1
  1. 1.School of Electronic and Electrical EngineeringUniversity of LeedsUK

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