Time-domain terahertz (THz) spectroscopy has been used to characterize polymorphic transformations in polycrystalline theophylline, a widely used pharmaceutical compound. On transformation, different intermolecular bonding arrangements arise owing to changes in the lattice structure of the molecular crystal, leading to distinct THz spectral signatures. Temperature-dependent THz absorption measurements in anhydrous theophylline confirm that the observed vibrational modes originate from phonons within the crystal structure.
Terahertz technology has shown great promise in recent years with a large number of applications being demonstrated, as well improvements in detectors, sources, imaging schemes. Many of the proposed applications, however, will require compact imaging systems that have the capability to capture two-or three-dimensional images. We propose an area-scan configuration that has the potential to meet this need that could be used to generate three-dimensional images through holographic techniques. We present data that verify the feasibility of our scheme.
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