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.

Terahertz time-domain spectroscopy characterization of the far-infrared absorption and index of refraction of high-resistivity, float-zone silicon

Abstract: The far-infrared absorption and index of refraction of high-resistivity, float-zone, crystalline silicon has been measured by terahertz time-domain spectroscopy. The measured new upper limit for the absorption of this most transparent dielectric material in the far infrared shows unprecedented transparency over the range from 0.5 to 2.5 THz and a well-resolved absorption feature at 3.6 THz. The index of refraction shows remarkably little dispersion, changing by only 0.0001 over the range from 0.5 to 4.5 THz.

Plasmon enhanced solar-to-fuel energy conversion.

Abstract: Future generations of photoelectrodes for solar fuel generation must employ inexpensive, earth-abundant absorber materials in order to provide a large-scale source of clean energy. These materials tend to have poor electrical transport properties and exhibit carrier diffusion lengths which are significantly shorter than the absorption depth of light. As a result, many photoexcited carriers are generated too far from a reactive surface and recombine instead of participating in solar-to-fuel conversion. We demonstrate that plasmonic resonances in metallic nanostructures and multilayer interference effects can be engineered to strongly concentrate sunlight close to the electrode/liquid interface, precisely where the relevant reactions take place. On comparison of spectral features in the enhanced photocurrent spectra to full-field electromagnetic simulations, the contribution of surface plasmon excitations is verified. These results open the door to the optimization of a wide variety of photochemical process...

Direct Measurement of Conjugated Polymer Electronic Excitation Energies Using Metal/Polymer/Metal Structures

Abstract: We report electroabsorption measurements of built-in electric fields and internal photoemission measurements of Schottky barriers to determine the charge transfer and single-particle energy gaps of the conjugated polymer poly[2-methoxy, 5-(2\ensuremath{'}-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV). For MEH-PPV, with an exciton absorption peak of 2.25 eV, or results yield a single-particle energy gap of 2.45 eV and a charge transfer energy gap of at least 2.35 eV. Therefore the exciton binding energy is 0.2 eV and the bipolaron binding energy is less than 0.1 eV.

Aharonov-Bohm effect in carbon nanotubes

Abstract: Optical absorption spectra are calculated in carbon nanotubes in the presence of a magnetic flux parallel to the tube axis. A drastic change in the band gap manifests itself in optical spectra for light polarization parallel to the axis. In the case of perpendicular polarization, the absorption is suppressed by a large depolarization effect.

Deconvolution of mineral absorption bands: An improved approach

Abstract: Although visible and near IR reflectance spectra contain absorption bands that are characteristic of the composition and structure of the absorbing species, deconvolving a complex spectrum is nontrivial. An improved approach to spectral deconvolution is presented that accurately represents absorption bands as discrete mathematical distributions and resolves composite absorption features into individual absorption bands. The frequently used Gaussian model of absorption bands is shown to be inappropriate for the Fe(2+) electronic transition absorptions in pyroxene spectra. A modified Gaussian model is derived using a power law relationship of energy to average bond length. The modified Gaussian model is shown to provide an objective and consistent tool for deconvolving individual absorption bands in the more complex orthopyroxene, clinopyroxene, pyroxene mixtures, and olivine spectra.