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.

Absorption Ångström coefficient, brown carbon, and aerosols: basic concepts, bulk matter, and spherical particles

Abstract: . The concept of wavelength-dependent absorption Angstrom coefficients (AACs) is discussed and clarified for both single and two-wavelengths AACs and guidance for their implementation with noisy absorption spectra is provided. This discussion is followed by application of the concept to models for brown carbon bulk absorption spectra including the damped simple harmonic oscillator model, its Lorentzian approximation, and the band-gap model with and without Urbach tail. We show that the band-gap model with Urbach tail always has an unphysical discontinuity in the first derivative of the AAC at the band-gap – Urbach-tail matching wavelength. Complex refractive indices obtained from the bulk damped simple harmonic oscillator model are used to calculate absorption spectra for spherical particles, followed by a discussion of their features. For bulk material and small particles, this model predicts a monotonic decrease of the AAC with wavelength well above the resonance wavelength; the model predicts a monotonic increase for large particles.

Hierarchical Carbon Fiber@MXene@MoS2 Core-sheath Synergistic Microstructure for Tunable and Efficient Microwave Absorption

Abstract: Microcosmic 3D hierarchical structural design has proved to be an effective strategy to obtain high‐performance microwave absorbers, although the treatments to low‐dimensional cells in monolithic framework are usually based on semiempirical rules. In this work, a hierarchical carbon fiber (CF)@MXene@MoS2 (CMM) core‐sheath synergistic structure with tunable and efficient microwave absorption (MA) properties is fabricated by introducing self‐assembled Ti3C2Tx MXene on the surface of CF and subsequent anchoring of MoS2. By the synergistic effects from the MXene sheath increasing the conductive loss and MoS2 at the outermost layer improving the impedance matching, the MA performance of CMM can be effectively regulated and optimized: the optimal reflection loss is −61.51 dB with a thickness of 3.5 mm and the maximum effective absorption bandwidth covers the whole Ku‐band with 7.6 GHz at 2.1 mm. Meanwhile, the whole X‐band absorption can also be achieved with specific MoS2 loading at an optimized thickness.

The optical properties of pure water

Abstract: The optical properties of pure water are basic input data for many geophysical investigations such as remote sensing of surface water and underwater radiative transfer calculations. Knowledge of the spectral properties of components in surface water is required for accurate interpretation ofmeasured reflection and attenuation spectra in terms oftheir concentrations. Also the sources and sizes of errors in the basic data must be known. Absorption measurements were done with a submersible absorption meter in the temperature range 2.5 till 40.5 °C. The scattering of pure water is recalculated using the Einstein-Smoluchowski equation. The input for this equation is evaluated and the temperature dependency is included. New values for the absorption coefficient are given based on these results and analysis of data from the literature. Absorption in the wavelength range 300-550 nm is lower than presently used values. In the wavelength range above 700 nm the spectrum has a different shape. A formulation of the effect of temperature on the absorption spectrum is given.

Effect of Axial Substitution on the Optical Limiting Properties of Indium Phthalocyanines

Abstract: Nonlinear absorption, refraction, and optical limiting by a series of monoaxially chloro- and aryl-substituted indium(III) phthalocyanines are described. The absorption cross sections and temporal evolution of the low-lying excited states are also reported. A large nonlinear absorption that increased with wavelength between 500 and 590 nm was observed in each material. The nanosecond nonlinear absorption and the optical limiting are shown to be dominated by a strong excited state absorption from an orientationally averaged triplet state. We derive and experimentally confirm the relation between the molecular absorption cross sections and the fluence-dependent nonlinear absorption coefficients. The effective nonlinear refraction on the nanosecond time scale was reduced because the electronic contribution to the nonlinear refractive index was of the opposite sign from the thermal contribution. An optical limiter using the new material, p-(trifluoromethyl)phenylindium(III) tetra-tert-butylphthalocyanine [(t-...

Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films.

Abstract: Atomically thin graphene/WS2/graphene heterostructures exhibit enhanced light—matter interactions, leading to enhanced photon absorption and electron—hole creation.