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Experimental infrared spectroscopic measurement of light extinction for agglomerate dust grains
Authors:Akemi Tamanai  Harald Mutschke  Jürgen Blum  Ralph Neuhuser
Institution:

aAstrophysical Institute and University Observatory, Friedrich-Schiller-University Jena, Schillergäßchen 3, D-07745 Jena, Germany

bInstitut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38106 Braunschweig, Germany

Abstract:Optical properties of aggregate dust grains hold a key to understand many astrophysical problems. Scattering and absorption features are strongly influenced by morphological aspects of grains (particle size, shape, and agglomeration). We have experimentally investigated the morphological effects on the View the MathML source extinction band in the infrared region for amorphous silica (SiO2) particles which are of 0.5, 1.0, and View the MathML source in diameter. Deviations of the peak position of this band have been detected depending on environment (air or KBr), particle size, and manufacturer of the samples. We found that the peak position difference of silica particles with a diameter of 0.5 and View the MathML source was View the MathML source in wavelength whereas the effect of different environments were approximately View the MathML source. In addition, the measured band profiles were compared with calculations for five cluster shapes applying three different theoretical approaches (Mie, T-matrix, and DDA). The calculated extinction efficiencies beyond the peaks rose as the particle size and the particle numbers in the clusters increased. The same rise compared to the Mie calculation was observed in the experimental spectra, which was, therefore, interpreted as a result of the clustering of the particles.
Keywords:Agglomerate  Silica  Extinction  Cluster
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