A New Method For Obtaining Optical Constants In The Near-IR To UV From Single-crystal Absorption Spectra: SiC And Silicates As Examples

Details A New Method For Obtaining Optical Constants In The Near-IR To UV From Single-crystal Absorption Spectra: SiC And Silicates As Examples A New Method For Obtaining Optical Constants In The Near-IR To UV From Single-crystal Absorption Spectra: SiC And Silicates As Examples

Jan 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21547602h&link_type=abstract

American Astronomical Society, AAS Meeting #215, #476.02; Bulletin of the American Astronomical Society, Vol. 42, p.523

Astronomy and Astrophysics

Astronomy

Scientific paper

An important constraint in dust models is visible to UV extinction, due to high photon flux occurring in this spectral region. Radiative transfer models of dust require knowing the frequency dependence of their optical functions, n and k, which are generally obtained from reflectivity measurements. However, constraining low values of reflectivity, as occurs in the visible, requires very large crystals; plus, absolute values of reflectivity are generally difficult to ascertain. We developed a method to accurately constrain both n and k from absorption measurements of single crystals. The method requires two identical crystals of different, well-constrained thickness, and smaller sizes than that needed for reflectivity. Cross-checks are made thru refractometry measurements of n in the visible, which are highly accurate. For highly absorbing regions, as is possible in the UV by cation-anion charge-transfer, reflectivity data can be incorporated in our method, or used as a cross-check. Extremely accurate values of n and k are obtained from our approach. Two examples are provided: SiC and forsterite. The visible-UV region is sensitive to impurities, and laboratory data may afford opportunity to probe chemical composition in astronomical environments.

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