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Absorption (electromagnetic radiation)

About: Absorption (electromagnetic radiation) is a research topic. Over the lifetime, 76674 publications have been published within this topic receiving 1381221 citations.


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Journal ArticleDOI
TL;DR: The absorption spectra of seventeen explosives and related compounds (ERCs) are investigated by using terahertz time-domain spectroscopy in the 0.1-2.8 THz region to form a database of these ERCs, of great importance for biochemical, defense and security related applications.
Abstract: We have investigated the absorption spectra of seventeen explosives and related compounds (ERCs) by using terahertz time-domain spectroscopy in the 0.1-2.8 THz region. Most of these substances show characteristic absorption features in this frequency range. The measured absorption coefficients of these ERCs form a database, which is of great importance for biochemical, defense and security related applications.

311 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present results from a 900 ks exposure of NGC 3783 with the High-Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory.
Abstract: We present results from a 900 ks exposure of NGC 3783 with the High-Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory. The resulting X-ray spectrum has the best combination of signal-to-noise and resolution ever obtained for an AGN. This spectrum reveals absorption lines from H-like and He-like ions of N, O, Ne, Mg, Al, Si, and S. There are also possible absorption lines from H-like and He-like Ar and Ca. We also identify inner-shell absorption from lower-ionization ions such as Si_VII-Si_XII and S_XII-S_XIV. The iron absorption spectrum is very rich; L-shell lines of Fe_XVII-Fe_XXIV are detected, strong complex of M-shell lines, and probable resonance lines from Fe_XXV. The absorption lines are blueshifted relative to the systemic velocity by a mean velocity of -590+-150 km/s. We resolve many of the absorption lines, and their mean FWHM is 820+-280 km/s. We do not find correlations between the velocity shifts or the FWHMs with the ionization potentials of the ions. Most absorption lines show asymmetry, having more extended blue wings than red wings. In O_VII we have resolved this asymmetry to be from an additional absorption system at ~ -1300 km/s. The two X-ray absorption systems are consistent in velocity shift and FWHM with the ones identified in the UV lines of C IV, N V, and H I. Equivalent width measurements for all lines are given and column densities are calculated for several ions. We resolve the narrow Fe_K\alpha line at 6398.2+-3.3 eV to have a FWHM of 1720+-360 km/s, which suggests that this narrow line may be emitted from the outer part of the broad line region or the inner part of the torus. We also detect a `Compton shoulder' redward of the narrow Fe_K\alpha line which indicates that it arises in cold, Compton-thick gas.

310 citations

Journal ArticleDOI
18 Apr 2011-ACS Nano
TL;DR: This paper demonstrates a conformal metamaterial absorber with a narrow band, polarization-independent absorptivity of >90% over a wide ±50° angular range centered at mid-infrared wavelengths of 3.3 and 3.9 μm, making it attractive for advanced coatings that suppress the infrared reflection from the protected surface.
Abstract: Metamaterials offer a new approach to create surface coatings with highly customizable electromagnetic absorption from the microwave to the optical regimes. Thus far, efficient metamaterial absorbers have been demonstrated at microwave frequencies, with recent efforts aimed at much shorter terahertz and infrared wavelengths. The present infrared absorbers have been constructed from arrays of nanoscale metal resonators with simple circular or cross-shaped geometries, which provide a single band response. In this paper, we demonstrate a conformal metamaterial absorber with a narrow band, polarization-independent absorptivity of >90% over a wide ±50° angular range centered at mid-infrared wavelengths of 3.3 and 3.9 μm. The highly efficient dual-band metamaterial was realized by using a genetic algorithm to identify an array of H-shaped nanoresonators with an effective electric and magnetic response that maximizes absorption in each wavelength band when patterned on a flexible Kapton and Au thin film substrat...

310 citations

Journal ArticleDOI
TL;DR: In this paper, a photothermal displacement spectroscopy (PDS) was proposed for determining the optical and thermal properties of solids, surfaces and thin films, based on the detection of the thermal expansion of a sample upon absorption of electromagnetic radiation.
Abstract: We present a sensitive technique for determining the optical and thermal properties of solids, surfaces and thin films. This technique, photothermal displacement Spectroscopy, is based on the detection of the thermal expansion of a sample upon absorption of electromagnetic radiation. The technique is well suited for in situ ultrahigh vacuum studies and for experiments where wide temperature ranges are required. We show that surface and bulk optical absorption can be distinguished and that surface absorptions of αL=10−6/W of incident power can be measured. The theoretical basis of the signal generation is given, and excellent experimental and theoretical agreement is demonstrated. The implications of our findings to imaging and microscopy are discussed.

310 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that both the magnitude and spectral dependence of light absorption are controlled by the size of graphitic clusters within the material, and can be described using the optical band-gap theory.
Abstract: Optical characteristics of particles that absorb visible light are needed to model their effects on atmospheric radiation. Light absorption by particles emitted from low-technology coal combustion has exhibited a strong spectral dependence. I investigate various explanations for this phenomenon and conclude that a spectrally dependent imaginary refractive index is the most plausible. Following previous work on the structure of amorphous carbon, I propose that both the magnitude and spectral dependence of light absorption are controlled by the size of graphitic clusters within the material, and can be described using the optical band-gap theory. This hypothesis is an alternative to the current measurement divisions of light-absorbing “black carbon” and non-absorbing “organic carbon,” and offers an explanation for preferential absorption at blue wavelengths that may extend to ultraviolet wavelengths.

310 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2022185
20213,106
20202,866
20192,953
20182,876
20172,679