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.

Plasmon–Exciton Interactions in a Core–Shell Geometry: From Enhanced Absorption to Strong Coupling

Abstract: We present a detailed Mie theory, finite-difference time-domain, and quasi-static study of plasmon–exciton interactions in a spherical core–shell geometry. In particular, we report absorption, scattering, and extinction cross sections of a hybrid core–shell system and identify several important interaction regimes that are determined by the electromagnetic field enhancement and the oscillator strength of electronic excitations. We assign these regimes to enhanced-absorption, exciton-induced transparency and strong coupling, depending on the nature of the observed spectra of the coupled plasmon–exciton resonances. We also show the relevance of performing single-particle absorption or extinction measurements in addition to scattering to validate the interaction regime. Furthermore, at relatively high, yet realistic oscillator strengths we observe emergence of a third mode, which is not predicted by a classical coupled harmonic oscillator model and is attributed to the geometrical resonance of the structure ...

Tunneling induced transparency: Fano interference in intersubband transitions

Abstract: We report the observation of tunneling induced transparency in asymmetric double quantum well structures. Resonant tunneling through a thin barrier is used to coherently couple the two upper states in a three level system of electronic subbands in a GaAs/AlGaAs structure. This creates Fano-type interferences for the collective intersubband excitations in the absorption from the ground state, analogous to electromagnetically induced transparency (EIT) in atomic systems. We observe a 50% reduction in absorption between the subband resonances which can be explained by taking into account the coherent coupling of the upper states. We analyze the bias dependent absorption spectra and determine the relevant lifetime broadening and dephasing rates for the transitions.

Effect of pigment composition on absorption properties of phytoplankton

Abstract: Absorption spectra of several phytoplankton species were decomposed, after correction for the particle effect, to estimate in vivo absorption properties of the major light-harvesting pigments in algae. A Gaussian shape is suitable, theoretically and empirically, to represent the absorption spectra of individual photosynthetic components. The Gaussian parameters agreed well with the expected pigment compositions of 3 groups of algae, and the peak heights were linearly correlated with the concentrations of any one of the 4 major pigments measured in the samples. The linear relationship did not vary with phytoplankton species. We present here the first estimates of the 'true' in vivo specific absorption coefficients of 4 major pigments, after correction for particle effect. The results are used to reconstruct the in vivo absorption spectrum of a multi-species sample.

The Location of Guaiacyl and Syringyl Lignins in Birch Xylem Tissue

Abstract: Spectral analysis with the UV microscope has revealed that the lignin associated with the vessel secondary wall and middle lamella of birch xylem is composed predominandy of guaiacylpropane units. Lignin deposited in the fibre and ray parenchyma secondary walls is composed mostly of syringylpropane units. The middle lamella lignin around fibres and ray cells contains both guaiacyland syringylpropane units.

Effective atomic number and energy absorption in tissues.

Abstract: An X-ray absorption method, using Ross balanced filters, is applied to measure the effective atomic number of excised body tissues. The results are used to calculate linear absorption coefficients and the true energy absorption in ergs per rontgen for these tissues over a wide range of wavelength. Approximate methods of calculation are applied to determine the dosage throughout a heterogeneous medium and a number of examples, relevant to clinical treatments, are worked out on an energy absorption basis. The problem of dosage in bone is considered and an attempt is made to extend the specification of radiation dosage beyond that stated in terms of the rontgen.