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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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TL;DR: In this article, the authors present new electronic absorption, electron microscopy, and X-ray absorption data in several systems to show that the near-infrared absorption does not involve core/shell structures.
Abstract: The reduction of HAuCl4 by Na2S has been reported to produce gold nanoparticles with an optical absorption in the near-infrared along with its characteristic absorption in the visible. The optical resonances in the visible are due to the gold surface plasma, which are a function of the geometry of the particles. The near-infrared absorption had been attributed to the formation of Au2S/Au core/shell structures. In this report we present new electronic absorption, electron microscopy, and X-ray absorption data in several systems to show that the near-infrared absorption does not involve core/shell structures. We further suggest that the near-infrared adsorption is most likely the result of the formation of aggregates of gold nanoparticles. The identification of the origin of the near-infrared resonance is critical in understanding the optical properties of metal nanoparticle systems.

241 citations

Journal ArticleDOI
TL;DR: In this article, the absorption and piginenting efficacy of carotenoids in rainbow trout was investigated. But no epimerization of astaxanthin at C(3)/C(3') was detected in rainbow fish, nor was there one in chicken after zeaxanthins administration.
Abstract: Absorption and piginenting efficacy of astaxanthin, canthaxanthin and zeaxanthin were studied in rainbow trout (Salmo crairdneri, R.). Astaxanthin is the best pigmenter, followed by canthaxanthin and astaxanthin dipalmitate. Metabolites present in the skin were isolated, identified and compared with those in the skin of Atlantic salmon (Salmo salar) . The di stribution of zeaxanthin and astaxanthin in the body of the chicken was also studied comparatively. Emphasis was laid on the configurational analysis of the administered carotenoids as well as of their metabolites. absorption and deposition of the single stereoisomers were compared. No epimerization of astaxanthin at C(3)/C(3') was detected in rainbow trout, nor was there one in chicken after zeaxanthin administration. A biological function of astaxanthin, canthaxanthin and zeaxanthin as vitamin A (retinol and 3,4-didehydroretinol) precursors was found in vitamin A depleted rainbow trout.

241 citations

Journal ArticleDOI
TL;DR: The dynamic control of thermal emission via the control of emissivity (absorptivity) is experimentally demonstrated, at a speed four orders of magnitude faster than is possible using the conventional temperature-modulation method.
Abstract: Thermal emission in the infrared range is important in various fields of research, including chemistry, medicine and atmospheric science. Recently, the possibility of controlling thermal emission based on wavelength-scale optical structures has been intensively investigated with a view towards a new generation of thermal emission devices. However, all demonstrations so far have involved the 'static' control of thermal emission; high-speed modulation of thermal emission has proved difficult to achieve because the intensity of thermal emission from an object is usually determined by its temperature, and the frequency of temperature modulation is limited to 10-100 Hz even when the thermal mass of the object is small. Here, we experimentally demonstrate the dynamic control of thermal emission via the control of emissivity (absorptivity), at a speed four orders of magnitude faster than is possible using the conventional temperature-modulation method. Our approach is based on the dynamic control of intersubband absorption in n-type quantum wells, which is enhanced by an optical resonant mode in a photonic crystal slab. The extraction of electrical carriers from the quantum wells leads to an immediate change in emissivity from 0.74 to 0.24 at the resonant wavelength while maintaining much lower emissivity at all other wavelengths.

240 citations

Journal ArticleDOI
TL;DR: In this article, a simulation of the absorption process for radiation of energy density E20/4πnT ranging from much less than to somewhat greater than unity has been performed, showing that the appearance of a finite density variation over the distance of a few Debye lengths is forced by strong gradients in the plasma wave intensity and electron temperature.
Abstract: Resonant absorption has been simulated for radiation of energy density E20/4πnT ranging from much less than to somewhat greater than unity. Characteristic features of the absorption process are an absorption efficiency of approximately 50%, generation of suprathermal particles, and strong modification of the density profile in the vicinity of the critical density. The latter effect, the appearance of a finite density variation over the distance of a few Debye lengths, is forced by strong gradients in the plasma wave intensity and electron temperature. Such a density discontinuity greatly enhances the range of incidence angles for which resonance absorption is effective and decreases the effects of the oscillating two‐stream and ion‐acoustic decay instabilities.

240 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