scholarly journals Поглощение электромагнитного излучения аморфным углеродом, модифицированным металлами

2021 ◽  
Vol 47 (2) ◽  
pp. 18
Author(s):  
С.Г. Ястребов ◽  
И.Е. Истомин ◽  
M. Singh
Keyword(s):  
Electromagnetic Wave ◽  
Radio Frequency ◽  
Electromagnetic Radiation ◽  
Amorphous Carbon ◽  
Cross Sections ◽  
Theoretical Study ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Structural Studies ◽  
Absorption Cross

This article presents a theoretical study of the scattering and absorption of an electromagnetic wave from the gigahertz to the red range for a model of amorphous carbon modified by metals. On the basis of structural studies of this material, a cylindrical anisotropic nanoparticle - a nanotube responsible for its absorbing and antireflection properties - was selected as a candidate. A model of such a particle was developed and the scattering and absorption cross sections of an electromagnetic wave were calculated within the framework of the theory of the discrete dipole approximation. A pair of nanotubes allowed us to explain the contribution of the interaction of immediate neighbors to scattering and absorption. The constructed model explains the effect of absorption of radio-frequency electromagnetic radiation, observed experimentally in amorphous carbon modified with metals.

scholarly journals Simulated Optical Properties of Gold Nanocubes and Nanobars by Discrete Dipole Approximation

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Mohammed Alsawafta ◽  
Mamoun Wahbeh ◽  
Vo-Van Truong
Keyword(s):  
Absorption Spectrum ◽  
Cross Section ◽  
Longitudinal Mode ◽  
Transverse Mode ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Absorption Cross ◽  
Extinction Cross Section ◽  
Band Position ◽  
Mode Tm

The absorption spectra for a gold nanocube and for a gold nanobar are calculated by using the Discrete Dipole Approximation (DDA). The results show the excitation of a single albeit broad surface plasmon (SP) band of the gold nanocube. The extinction cross section of the gold nanocube is dominated by the absorption cross section that gains importance as the width increases. Further increasing the nanocube size beyond 80 nm will result in an optical response mainly characterized by scattering properties. The absorption spectrum of the nanobar shows the excitation of both the longitudinal mode (LM) and the transverse mode (TM). The nanobar is also compared to a cylinder, a spherically capped cylinder, and a spheroid of the same aspect ratio. The band position of the TM of the nanobar is red-shifted as compared to the ones calculated for other morphologies, while the LM is either blue-shifted or red-shifted depending on the morphologies considered.

scholarly journals On the absorption properties of metallic needles

2020 ◽  
Vol 498 (3) ◽  
pp. 3560-3564
Author(s):  
C Y Xiao ◽  
Qi Li ◽  
Aigen Li ◽  
J H Chen
Keyword(s):  
Cross Sections ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Interstellar Extinction ◽  
Wavelength Dependence ◽  
Dipole Approximation ◽  
Absorption Cross ◽  
Absorption Properties ◽  
Aspect Ratios ◽  
Iron Whiskers

ABSTRACT Needle-like metallic particles have been suggested to explain a wide variety of astrophysical phenomena, ranging from the mid-infrared interstellar extinction to the thermalization of starlight to generate the cosmic microwave background. These suggestions rely on the amplitude and the wavelength dependence of the absorption cross-sections of metallic needles. On the absence of an exact solution to the absorption properties of metallic needles, their absorption cross-sections are often derived from the antenna approximation. However, it is shown here that the antenna approximation is not an appropriate representation, since it violates the Kramers–Kronig relation. Stimulated by the recent discovery of iron whiskers in asteroid Itokawa and graphite whiskers in carbonaceous chondrites, we call for rigorous calculations of the absorption cross-sections of metallic needle-like particles, presumably with the discrete dipole approximation. We also call for experimental studies of the formation and growth mechanisms of metallic needle-like particles as well as experimental measurements of the absorption cross-sections of metallic needles of various aspect ratios over a wide wavelength range to bound theoretical calculations.

scholarly journals Composite interstellar grains and the 2175Å feature

2008 ◽  
Vol 4 (S251) ◽  
pp. 77-78
Author(s):  
Deepak B. Vaidya ◽  
Ranjan Gupta
Keyword(s):  
Cross Sections ◽  
Wavelength Region ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Interstellar Grains ◽  
Grain Model ◽  
Graphite Inclusions

AbstractWe use discrete dipole approximation (DDA) to study the scattering properties of composite grains made up of host silicate spheroids and graphite inclusions. We calculate the extinction cross sections of the composite grains in the wavelength region 0.20–0.55 μm and study the extinction of the composite grains as a function of graphite inclusions. We present the composite grain model and discuss the results.

scholarly journals Experimental and theoretical study of light scattering by individual mature red blood cells by use of scanning flow cytometry and a discrete dipole approximation

2005 ◽  
Vol 44 (25) ◽  
pp. 5249 ◽  
Author(s):  
Maxim A. Yurkin ◽  
Konstantin A. Semyanov ◽  
Peter A. Tarasov ◽  
Andrei V. Chernyshev ◽  
Alfons G. Hoekstra ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Light Scattering ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Theoretical Study ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation

scholarly journals Optical properties of elongated conducting grains

2021 ◽  
Vol 503 (3) ◽  
pp. 4544-4550
Author(s):  
X M Huang ◽  
Qi Li ◽  
Aigen Li ◽  
J H Chen ◽  
F Z Liu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Cross Sections ◽  
Interstellar Extinction ◽  
Wavelength Dependence ◽  
Dipole Approximation ◽  
Dust Particles ◽  
Absorption Cross ◽  
Microwave Background ◽  
Rayleigh Approximation ◽  
Aspect Ratios

ABSTRACT Extremely elongated, conducting dust particles (also known as metallic ‘needles’ or ‘whiskers’) are seen in carbonaceous chondrites and in samples brought back from the Itokawa asteroid. Their formation in protostellar nebulae and subsequent injection into the interstellar medium have been demonstrated, both experimentally and theoretically. Metallic needles have been suggested to explain a wide variety of astrophysical phenomena, ranging from the mid-infrared interstellar extinction at $\sim \,$3–8$\, {\rm \mu m}$ to the thermalization of starlight to generate the cosmic microwave background. To validate (or invalidate) these suggestions, an accurate knowledge of the optics (e.g. the amplitude and the wavelength dependence of the absorption cross sections) of metallic needles is crucial. Here we calculate the absorption cross sections of iron needles of various aspect ratios over a wide wavelength range, by exploiting the discrete dipole approximation, the most powerful technique for rigorously calculating the optics of irregular or nonspherical grains. Our calculations support the earlier findings that the antenna theory and the Rayleigh approximation, which are often taken to approximate the optical properties of metallic needles, are indeed inapplicable.

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