Contribution to interstellar extinction from an astrophysical microsoot?

The optical constants of a carbon polymorph, calculated using the Drude dispersion theory, are shown to lead to close agreements with the mean interstellar extinction curve over the waveband 0.3 ≤ λ-1 ≤ 5.5 μm-1 for particles of Rayleigh scattering sizes. Astrophysical microsoot grains of radii ≤50A may be related to microdiamond grains of similar sizes that have recently been discovered in carbonaceous chondrites. It is postulated that such microsoot particles could contribute to the nearly invariable interstellar extinction law observed over the near IR, visible and near to mid UV spectral regions. Admixtures of microsoot with micron-sized microsoot clumps, microdiamond and hollow organic / biologic grains provide an explanation for the full range of extinction and polarization data.