Optical properties of oxide dust grains

Publication

Reference: Henning Th., Begemann B., Mutschke H., Dorschner J. (1995). Optical properties of oxide dust grains. Astron. Astrophys. Suppl., 112, 143 - 149.

Names

Title: Optical properties of oxide dust grains
Abstract: In this paper, we present the optical properties of a series of well-characterized metal oxides ($Fe_xMg_{1-x}O$, x=1.0, 0.9, 0.8, 0.7, 0.5, 0.4) in the wavelength range from 200nm to 500μm. A number of oxygen-rich stars show circumstellar dust features between 10 and 14μm and around 19μm which cannot be explained by ordinary cosmic silicates but may be modelled by a mixture of aluminium oxide and iron-magnesium oxides. Calculated absorption spectra for small spheres show one vibrational band in the range from 19.9μm ($FeO$) to 17.7μm ($Fe_{0.4} Mg_{0.6}O$) in the Rayleigh limit. The absolute peak values of the oxide absorption bands are more than a factor of two larger than the 18μm band of amorphous silicates, indicating that a small admixture of oxides can change the 18μm/10μm band ratio dramatically. The near-infrared opacity of the iron-rich oxides is of comparable magnitude to that of $Fe_3O_4$. Therefore, small amounts of iron-rich oxides in addition to silicates raise the absorbance in this spectral range in a very efficient way.
Keywords: optical constants, infrared, visible, reflectance, oxides
Content: instrument-technique, material-matter, spectral data, spectral data use

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