Attenuation contrast between biomolecular and inorganic materials at terahertz frequencies

Wideband photomixing spectroscopy is used in the present work to contrast the transmission spectra of macromolecules commonly found in biomaterials such as potato starch, wheat flour and cornstarch, and proteins (Cytoplex(TM)), and micromolecules such as sucrose, and inorganic materials such as sodium bicarbonate, and calcium sulfate. Powdered samples were measured at 0.1-0.5 THz frequencies. A significant difference in attenuation is found between these samples. At 300 GHz starch shows an absorption coefficient of similar to6 cm(-1) whereas Cytoplex shows 1-3 cm(-1), while inorganic micromolecules have similar to1 cm(-1). The absorption in starch increases rapidly with frequency tending to follow a power law alpha=f(n) with n typically between 1.5 and 2.0. In contrast, protein materials display a slower dependence on frequency with n between 1.0 and 1.5, and simple molecules show the least n among all three categories. The difference between these ubiquitous macromolecular and micromolecular materials is explained in terms of water content and molecular structure. (C) American Institute of Physics.