Topic
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 outline the current understanding of two general aspects of optical response of graphene: optical absorption and light emission, and show that optical absorption in graphene is dominated by intraband transitions at low photon energies and by interband transitions at higher energies (from mid-infrared to ultraviolet).
643 citations
TL;DR: In this article, the authors show that surface moisture content, organic matter, and particle size strongly influence the reflectance and absorptance of solar radiant energy by soils, and apply the kaolinite reflectance data to Gates' direct solar energy distribution curve, one would expect energy absorption to increase by at least an additional 14.6 percent of that in the incident beam when the particle size is increased from 22 mu to 2650 mu.
Abstract: Data secured with spectrophotometers show that surface moisture content, organic matter, and particle size strongly influence the reflectance and absorptance of solar radiant energy by soils. At all wavelengths measured, on all samples, reflectance decreased and absorptance increased as moisture content increased. By using Gates' direct solar energy distribution curve, one would expect that increasing the moisture content on a Newtonia silt loam from 0.8 to 20.2 percent would increase absorption of radiant energies by at least 14.2 percent of that in the equivalent direct solar beam. The plot of moisture content against reflectance indicates the possibility of using reflectance methods for surface moisture determinations. Results were especially good at 1900 mu, a moisture-sensitive wavelength. The oxidation of soil organic matter increased the reflectance from all samples measured. Again using Gates' distribution curve, 8.2 percent more of the energy in the equivalent direct solar beam might have been reflected by the oxidized Newtonia silt loam sample. With both kaolinite and bentonite clays, reflectance increased exponentially as particle size decreased. The magnitude of reflectance change was very similar with both clays. By applying the kaolinite reflectance data to Gates' direct solar energy distribution curve, one would expect energy absorption to increase by at least an additional 14.6 percent of that in the incident beam when the particle size is increased from 22 mu to 2650 mu. /Author/
642 citations
TL;DR: Erbium-doped sodium yttrium fluoride (NaYF4:Er3+) up-conversion phosphors were attached to the rear of a bifacial silicon solar cell to enhance its reponsivity in the near-infrared.
Abstract: Erbium-doped sodium yttrium fluoride (NaYF4:Er3+) up-conversion phosphors were attached to the rear of a bifacial silicon solar cell to enhance its reponsivity in the near-infrared. The incident wavelength and light intensity were varied and the resulting short circuit current of the solar cell was measured. A close match between the spectral features of the external quantum efficiency and the phosphor absorption is consistent with the energy transfer up-conversion process. The peak external quantum efficiency of the silicon solar cell was measured to be (2.5±0.2)% under 5.1 mW laser excitation at 1523 nm, corresponding to an internal quantum efficiency of 3.8%.
633 citations
632 citations
TL;DR: In this paper, the authors used the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) pre-flight model satellite spectrometers to measure the gas-phase absorption spectra of the most important atmospheric trace gases (O3, NO2, SO2, O2, H2O, CO, CO2, CH4, and N2O) in the 230-2380 nm range at medium spectral resolution and at several temperatures between 203 and 293
Abstract: Using the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) pre-flight model satellite spectrometer, gas-phase absorption spectra of the most important atmospheric trace gases (O3, NO2, SO2, O2, OClO, H2CO, H2O, CO, CO2, CH4, and N2O) have been measured in the 230–2380 nm range at medium spectral resolution and at several temperatures between 203 and 293 K. The spectra show high signal-to-noise ratio (between 200 up to a few thousands), high baseline stability (better than 10−2) and an accurate wavelength calibration (better than 0.01 nm) and were scaled to absolute absorption cross-sections using previously published data. The results are important as reference data for atmospheric remote-sensing and physical chemistry. Amongst other results, the first measurements of the Wulf bands of O3 up to their origin above 1000 nm were made at five different temperatures between 203 and 293 K, the first UV-Vis absorption cross-sections of NO2 in gas-phase equilibrium at 203 K were recorded, and the ultraviolet absorption cross-sections of SO2 were measured at five different temperatures between 203 and 296 K. In addition, the molecular absorption spectra were used to improve the wavelength calibration of the SCIAMACHY spectrometer and to characterize the instrumental line shape (ILS) and straylight properties of the instrument. It is demonstrated that laboratory measurements of molecular trace gas absorption spectra prior to launch are important for satellite instrument characterization and to validate and improve the spectroscopic database.
630 citations