Database of Aerosol Spectra for Cosmic Dust
- No plots added in the last four weeks.
This new part of our databases contains measured infrared extinction spectra of powders dispersed in nitrogen gas.
In contrast to liquid or solid carriers, the electromagnetic interaction of the particles with the carrier gas is negligible, making the spectra and especially the band profiles equivalent to those of particles in space (vacuum).
"Extinction" is the optical depht being the result of absorption and scattering by the powder. For grains much smaller than the wavelenght, scattering is negligible and the spectrum is representative of the wavelenght-dependent emissivity of the particles as well.
The spectra are given as plots of the measured "extinction" versus wavelenght and as two-column tables containing wavelenght in micron and measured "extinction" in arbitrary units (links next to the figures). Note that the extinction values are non-quantitative, which is due to the limitations of the experimental method. for purpose of quantitative analyses they have to be scaled using a quantitative spectrum of a similar powder, either a calculated or an experimental one (e.g. of embedded materials). Note that the band profiles will be different and that a good scaling citerion is the integral over the band (although not absolutely exact). We give some recommendations for scaling in the additional information related to the spectra.
One purpose of the database is to provide spectra for different powder geometries (i.e. grain sizes, shapes, and states of agglomeration). Therefore, the spectra are generally accompanied by electron micrographs (SEM) of the particles as filtered from the carrier gas and often by higher resolution images (TEM) characterizing the grain shape in more detail.
Last modified: David Schmitz, 15. Aug 2008