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.
Papers published on a yearly basis
Papers
More filters
TL;DR: A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels as discussed by the authors.
Abstract: [1] A dual-wavelength photoacoustic instrument operating at 405 and 870 nm was used during the 2006 Fire Lab at Missoula Experiment to measure light scattering and absorption by smoke from the combustion of a variety of biomass fuels. Simultaneous measurements of aerosol light scattering by reciprocal nephelometry within the instrument's acoustic resonator accompany photoacoustic aerosol light absorption measurements. Single scattering albedo values at 405 nm ranging from 0.37 to 0.95 were measured for different fuel types, and the spectral dependence of absorption was quantified using the Angstrom exponent of absorption. An absorption Angstrom exponent near unity is commonly observed for motor vehicle emission-generated black carbon aerosol. For biomass smoke, Angstrom exponents as high as 3.5 were found in association with smoke having single scattering albedo near unity. The measurements strongly suggest that light-absorbing organic material is present in wood smoke. A second single-wavelength photoacoustic instrument with reciprocal nephelometry was used to quantify aerosol scattering and absorption at 532 nm. Absorption Angstrom exponents calculated using 532 and 870 nm data were as large as 2.5 for smoke with single scattering albedos near unity. The spectral variation in optical properties provides insight into the differentiation of aerosols from mobile or industrial sources versus those from biomass burning. Optical properties of biomass smokes could be classified by general fuel type such as flowering shrubs versus pine needle litter.
290 citations
TL;DR: In this paper, the effects of particle size, mineral mixtures, and viewing geometry for selected materials with well-developed absorption bands were analyzed using a new laboratory facility, the RELAB.
Abstract: Bidirectional reflectance measurements are the only type of reflectance data available to the remote observer. For compositional interpretations, data are desired not only for identification of possible mineral components but also for modal abundance. The latter requires detailed information about the strength of absorption features. Using a new laboratory facility, the RELAB, laboratory data in the near infrared are presented that document effects of particle size, mineral mixtures, and viewing geometry for selected materials with well-developed absorption bands. The commonly observed increase in reflectance with decrease in particle size is also observed for absorption bands as well as a related decrease in absorption strength. For small particles in parts of the spectrum of maximum reflectance, however, a minor decrease in reflectance with a decrese in particle size is sometimes observed. Small particles dominate the observed characteristics of particulate surfaces, which contain a range of particle sizes. The mean optical path length (transmission through particles) of reflected radiation measured for a variety of particle sizes has an apparent upper limit of about 2 mm for particles of less than 250 microns. The typical number of particles involved in the optical path is less than 50.
289 citations
TL;DR: In this article, the authors measured the photocurrent as a function of wavelength and found several peaks that coincide with optical absorption bands predicted by ligand field theory and SCF-Xα calculations.
289 citations
289 citations
08 Apr 1999
TL;DR: Cavity-ring-down spectroscopy is an emerging method for making high sensitivity absorption measurements with gas-phase samples as mentioned in this paper, and it has been widely used in the literature.
Abstract: Cavity-ring-down spectroscopy is an emerging method for making high sensitivity absorption measurements with gas-phase samples. This volume covers the history, theory, and numerous applications.
289 citations