Other
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........38r&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF TORONTO (CANADA), 1993.Source: Dissertation Abstracts International, Volume: 54-09, Section: B, pa
Other
2
Light Extinction
Scientific paper
Three approaches are developed to elucidate the effects of shape and clustering on the extinction of light by small dust particles. Particular emphasis is placed on amorphous carbon, a material of considerable astronomical interest. The first approach involves implementation of a self-consistent method for determining optical constants over a wide range in energy which combines extinction data in the infrared with other measurements relating to optical constants at higher energy. This method is applied to laboratory soot samples, assuming that a simple shape distribution (CDE) characterizes the optical properties of this dust. The effects of shape on the optical constants and on the extinction per unit volume are found to be significant. The second approach is to model clustering by an effective medium method in which a cluster is replaced by an equivalent sphere whose effective dielectric function varies with radius. Models are found in which the volume extinction efficiency is high, although not quite as high as in the first approach involving the CDE shape distribution. Self -consistent optical constants are also derived for a soot sample using these models. It is argued that only the most efficient cluster models can reproduce the large extinction observed for that particular sample. The third approach begins by describing two numerical methods solving the electromagnetic equations directly and introducing two new ones. Some of these methods are compared by applying them to test cases, mostly in the zero frequency limit for medium and large optical constants. Using some of these methods, proximity effects are investigated for the case of two nearby spheres. These effects, characterized by an enhancement in the extinction per unit volume compared to isolated spheres, are found to be most important at close separations. The results are also expressed in terms of a normal mode analysis. As more spheres are added to the system there is a further growth in the extinction enhancement. This growth is examined with respect to the topology of the arrangements, including compact clusters and irregular chains of spheres. The extinction produced is found to be important. A comparison between these various approaches yields a paradox that is discussed briefly.
No associations
LandOfFree
Shape and Clustering Effects on the Extinction of Light by Amorphous Carbon Grains does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Shape and Clustering Effects on the Extinction of Light by Amorphous Carbon Grains, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shape and Clustering Effects on the Extinction of Light by Amorphous Carbon Grains will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1264390