SHAPE AND CLUSTERING EFFECTS ON THE OPTICAL-PROPERTIES OF AMORPHOUS-CARBON

Optical constants for some samples of amorphous carbon are presented for the energy range 4.1 x 10(-3) to 3.5 x 10(3) eV, using a self-consistent method which combines extinction data in the infrared with other measurements of optical constants at higher energy. By construction, the optical constants satisfy the Kramers-Kronig relations. The effects of shape and clustering on the optical constants are examined and found to be significant. The CDE shape distribution mimics qualitatively the effects of compact clusters. Other data showing how the optical properties depend on the degree of hydrogenation and on the type of bonding in the amorphous carbon are discussed. Further laboratory measurements are suggested. The relevance of these optical constants to circumstellar and interstellar grains is reviewed.