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16-80 μm Spectra of Crystalline Silicates at 4 K, ~ 80 K and 295 K

Bowey, J. E., Lee, C., Tucker, Carole, Hofmeister, A. M. and Ade, Peter A. R. 2000. 16-80 μm Spectra of Crystalline Silicates at 4 K, ~ 80 K and 295 K. Presented at: ISO beyond the Peaks, Villafranca del Castillo, Spain, 2-4 February 2000. ISO Beyond the Peaks: Proceedings of the Second ISO Workshop on Analytical Spectroscopy : ISO Data Centre, Villafranca del Castillo, Madrid, Spain, 2-4 February 2000. ESASP , vol. 456. Paris: European Space Agency, pp. 339-342.

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Far-infrared laboratory spectra are normally taken at room temperature. However, the grains responsible for the >20 μm silicate emission bands in ISO spectra are at temperatures below ~ 150 K. Therefore we are conducting a comparative study of the absorption spectra of crystalline olivines, pyroxenes and hydrous silicates at 4 K, 80 K and at room temperature (295 K). Many bands become narrower and some bands split at cryogenic temperatures. Therefore, to resolve fine structure at 4 K the resolution must be increased to 0.25 cm-1 whilst 2 cm-1 resolution is adequate at 295 K. In general, 295 K bands are shifted to shorter wavelengths at 4 K; the magnitude of the shift increases with wavelength from ~ 0.1-0.2 μm for peaks near 25 μm to nearly ~ 1 μm for peaks between 70 and 80 μm. However, neighbouring bands are shifted by different amounts and the shift pattern varies between mineral groups. A ~ 80 K forsterite spectrum indicates that the 295 K-to-80 K wavelength shifts are smaller than the 295 K-to-4 K shift. Further measurements are being undertaken.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Silicate dust: Crystalline; Infrared Spectroscopy; Dust physics: Temperature
Publisher: European Space Agency
ISBN: 9789290926658
ISSN: 0379-6566
Last Modified: 04 Jun 2017 04:58

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