Elimination of scattering effects in spectral measurement of granulated materials using terahertz pulsed spectroscopy

摘要

Spectral distortions are commonly observed in terahertz spectra of granulated materials. These spurious structures in the spectroscopy are caused by scattering due to the refractive index mismatch between the particles and their surrounding medium. We find that the scattering contribution is random across sample positions and could be eliminated by summing and averaging multiple measurements over a sample area. We present experimental results of both absorbing and nonabsorbing particles in the size range 50-250 μm and also give an empirical expression to describe the effect of grain size on the scattering-induced extinction as a function of frequency.