Particle characterization using THz spectroscopy

Abstract

THz extinction spectroscopy extends UV-Vis and NIR-spectroscopy to characterize particles from fine powders and dust to sand, grains and granulated materials. We extract particle sizes from the spectral position of the first peak of the interference structure and size distributions from the visibility of the fine ripple structure in the measured extinction spectra. As such, we can demonstrate a route for a quick determination of these parameters from single measurements.Comment: 6 pages, 6 figure

Thermal Treatment of Chromium(III) Oxide with Carbonates Analyzed by Far-Infrared Spectroscopy

“…With an increasing average particle size of the PE powder, a decreasing infrared radiation transparency was detected, with the high energy cutoff wavenumber almost reciprocal to the grain size of the PE powder. 10 Thus, higher grain sizes of the PE powder result in stronger scattering of the infrared radiation whereby more IR radiation is lost. Figure 3 shows Figure 4 shows the far-IR spectra of the reaction products of these thermal The major product of the thermal treatment of Cr 2 O 3 with CaCO 3 at 1000 8C is the Cr(V) compound Ca 3 Cr 2 O 8 (=Ca 3 (CrO 4 ) 2 ).…”

“…With an increasing average particle size of the PE powder, a decreasing infrared radiation transparency was detected, with the high energy cutoff wavenumber almost reciprocal to the grain size of the PE powder. 10 Thus, higher grain sizes of the PE powder result in stronger scattering of the infrared radiation whereby more IR radiation is lost.…”

Analysis of granular packing structure by scattering of THz radiation

“…The spectral range of the setup directly determines the particle sizes and correlation lengths that can be investigated, thus a broad spectral range is highly desirable. High resolution, however, might be interesting for characterization of particles, as a fine ripple structure in the scattering spectra give information on size distributions 10 . Resolution is usually not an issue for characterization of packings, as F (| q|) and S(| q|) do not show abrupt changes or steep gradients (compare Sec.…”

“…In the intermediate regime, as no approximate formulas are available, knowledge of the complex refractive index of the particles is required for particle size analysis from measured scattering patterns. The nontrivial dependence of the scattering efficiency on the particle size in this intermediate regime additionally allows for particle size analysis by spectroscopic methods 10 .…”

THz Electron Paramagnetic Resonance / THz Spectroscopy at BESSY II

“…Apart from paramagnetic and molecular systems, as illustrated by Fig.3, the setup extends conventional static high eld FTIR spectroscopy in solids, powders and granular matter (Born et al, 2015;Vogel et al, 2015) to very low wavenumbers (3 cm −1 ), which are only accessible at CSR sources at su cient dynamic range. Moreover, the special time structure of THz emission in BESSY II's low alpha mode as well as from Laser-Energy Modulation (Slicing) allows for time-domain experiments revealing ultrafast (sub-ps) charge carrier and phonon dynamics in thin lms also under very high magnetic elds.…”