The contribution of carbon nanoparticles to the interstellar optical extinction

Abstract

The contribution from different types of nanocluster is examined as being responsible for the inhomogeneous broadening in the normalized interstellar extinction curve. These are (i) molecules of aromatic hydrocarbons, (ii) particles of amorphous (diamond-like) carbon, (iii) particles of glassy carbon, (iv) particles of amorphous carbon encapsulated in glassy carbon and (v) particles of amorphous carbon containing graphitized inclusions. It is shown that particles of encapsulated amorphous carbon together with particles of glassy carbon may contribute to the absorption band at 217.5 nm (5.67 eV) for a ratio between the size of the amorphous carbon core to its overall exterior in the range 0.6–0.8. Particles of amorphous diamond-like carbon containing graphitized inclusions may contribute both to the 217.5-nm absorption band and to the absorption band located at ∼400 nm (3.09 eV).