The discrete-dipole approximation and its application to interstellar graphite grains
1,467
Citation
0
Reference
10
Related Paper
Citation Trend
Abstract:
view Abstract Citations (996) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Discrete-Dipole Approximation and Its Application to Interstellar Graphite Grains Draine, B. T. Abstract The discrete dipole approximation (DDA), a flexible method for computing scattering of radiation by particles of arbitrary shape, is extended to incorporate the effects of radiative reaction and to allow for possible anisotropy of the dielectric tensor of the material. Formulas are given for the evaluation of extinction, absorption, scattering, and polarization cross sections. A simple numerical algorithm based on the method of conjugate gradients is found to provide an efficient and robust method for obtaining accurate solutions to the scattering problem. The method works well for absorptive, as well as dielectric, grain materials. Two validity criteria for the DDA are presented. The DDA is then used to compute extinction cross sections for spherical graphite grains and to calculate extinction cross sections for nonspherical graphite grains with three different geometries. It is concluded that the interstellar 2175 A extinction feature could be produced by small graphite grains which should have aspect ratios not far from unity. Publication: The Astrophysical Journal Pub Date: October 1988 DOI: 10.1086/166795 Bibcode: 1988ApJ...333..848D Keywords: Computational Astrophysics; Cosmic Dust; Discrete Functions; Graphite; Interstellar Space; Absorption Cross Sections; Grain Size; Polarization (Waves); Radiative Transfer; Scattering Cross Sections; Astrophysics; INTERSTELLAR: GRAINS; POLARIZATION; RADIATIVE TRANSFER full text sources ADS |Keywords:
Discrete dipole approximation
Extinction (optical mineralogy)
Cite
Extinction (optical mineralogy)
Carbon fibers
Component (thermodynamics)
Cite
Citations (9)
Extinction (optical mineralogy)
Ultraviolet
Cite
Citations (6)
The 2175 {\AA} ultraviolet (UV) extinction bump in interstellar medium (ISM) of the Milky Way was discovered in 1965. After intensive exploration of more than a half century, however, its exact origin still remains a big conundrum that is being debated. Here we propose a mixture model by which the extinction bump in ISM is argued possibly relevant to the clusters of hydrogenated T-carbon (HTC) molecules (C40H16) that have intrinsically a sharp absorption peak at the wavelength 2175 {\AA}. By linearly combining the calculated absorption spectra of HTC mixtures, graphite, MgSiO3 and Fe2SiO4, we show that the UV extinction curves of optional six stars can be nicely fitted. This present work poses an alternative explanation toward understanding the physical origin of the 2175 {\AA} extinction bump in ISM of the Milky Way.
Extinction (optical mineralogy)
Cite
Citations (13)
Extinction (optical mineralogy)
Particle (ecology)
Cite
Citations (0)
Interstellar ice
Amorphous carbon
Dark nebula
Carbon fibers
Cite
Citations (140)
Dust originates in near-stellar regions and is ejected into interstellar space. However, near-stellar dust is not the same as interstellar dust, because various processes operating in the interstellar medium tend to modify the physical and chemical nature of dust. Thus, dust evolves in interstellar space. In hot post-shock gas, dust grains may be shattered or even vaporized in grain–grain collisions, and eroded in gas–grain impacts. These destructive processes can be opposed by grain growth in cooler, denser regions of interstellar space. Starlight can modify the physical and chemical nature of some forms of dust. Higher temperatures tend to promote the conversion of amorphous material to crystalline, while fast particles in the form of cosmic rays tend to drive the reverse transition.
Interstellar ice
Dust lane
Starlight
Cite
Citations (0)
A model of interstellar dust must satisfy two conditions: dust grains have to be of the reasonable structure and chemical composition and explain basic observations. The latter are the interstellar extinction law and the depletion of interstellar elements. In this work, a new model of composite dust grains is considered. To calculate cross-sections of such particles the exact theory of light scattering by multi-layered grains is used. The results of modeling are compared with observations of the interstellar extinction toward the stars ‘ Oph and θ 1 v C Ori.
Extinction (optical mineralogy)
Cite
Citations (0)
The infrared extinction performances of round graphite flakes are calculated with discrete dipole approximation(DDA) method.Results show that the round flakes with diameter of 3-4 micrometers and thickness of one-tenth of diameter have better extinction performances in the middle and far infrared wavelengths,and that the extinction is mainly due to scattering.The round flakes have better extinction performances than spheres with the same effective radius.The thinner the thickness of round flakes,the bigger the extinction coefficient,and it will tend gradually to the maximum.
Extinction (optical mineralogy)
Discrete dipole approximation
Molar absorptivity
Cite
Citations (0)
Extinction (optical mineralogy)
Circumstellar dust
Intergalactic dust
Dark nebula
Cite
Citations (0)
Discrete dipole approximation (DDA) is used to cal- culate extinction efciencies of porous silicate and graphite grains. We apply DDA rst to the spheroidal solid grains as- sumed to be made of a large number of small scattering ele- ments (dipoles). Then we systematically reduce the number of dipoles to model the porous grains. The extinction is studied as a function of wavelength, grain size and porosity for both silicate and graphite grains. Finally the extinction efciencies of the porous silicate and graphite grains are used to evaluate the interstellar extinction curve which is found to t well with the average observed extinction curve.
Extinction (optical mineralogy)
Discrete dipole approximation
Cite
Citations (8)