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.

The Scattering Error Correction of Reflecting-Tube Absorption Meters

Abstract: In this paper we examine correction methods for the scattering error of reflecting tube absorption meters and spectrophotometers. We model the scattering error of reflecting tube absorption meters for different tube parameters and different inherent optical properties. We show that the only reasonable correction method for an absorption meter without attenuation measurements or a spectrophotometer is the method in which the measured absorption at a wavelength in the near infrared is subtracted. A better correction is obtained if attenuation is measured simultaneously and the absorption at the reference wavelength is multiplied by the ratio of the measured scattering at the measurement wavelength divided by the measured scattering coefficient at the reference wavelength. This is the proportional method. We showed that the important geometrical parameters of the reflecting tube can be obtained by a comparison of measurements and models of polystyrene beads. Finally we examine the improvements that could be obtained if a direct scattering measurement were made simultaneously with the absorption and attenuation measurements.

Electromagnetically induced transparency and absorption in metamaterials: the radiating two-oscillator model and its experimental confirmation.

Abstract: Several classical analogues of electromagnetically induced transparency in metamaterials have been demonstrated. A simple two-resonator model can describe their absorption spectrum qualitatively, but fails to provide information about the scattering properties-e.g., transmission and group delay. Here we develop an alternative model that rigorously includes the coupling of the radiative resonator to the external electromagnetic fields. This radiating two-oscillator model can describe both the absorption spectrum and the scattering parameters quantitatively. The model also predicts metamaterials with a narrow spectral feature in the absorption larger than the background absorption of the radiative element. This classical analogue of electromagnetically induced absorption is shown to occur when both the dissipative loss of the radiative resonator and the coupling strength are small. These predictions are subsequently demonstrated in experiments.

The propagation of electromagnetic energy through an absorbing dielectric

Abstract: The energy associated with an electromagnetic wave passing through a dielectric resides partly in the electromagnetic field and partly in the accompanying excitation of the dielectric. The theory of energy propagation through an absorbing classical dielectric having a single resonant frequency is presented in this paper. Simple expressions are derived for the velocity of energy transport associated with an electromagnetic wave, and for the finite energy relaxation time caused by the damping mechanism. The variations of these quantities, and of the absorption coefficient, with the relative values of the damping constant and dipole moment of the classical oscillator are investigated. This information is used to throw light on the basic mechanism of irreversible dissipation of energy by an electromagnetic wave in a dielectric. The similarities between the calculations of the dielectric constant by classical dispersion theory and by quantum mechanics are discussed.

Time-resolved x-ray absorption spectroscopy with a water window high-harmonic source

Abstract: Time-resolved x-ray absorption spectroscopy (TR-XAS) has so far practically been limited to large-scale facilities, to subpicosecond temporal resolution, and to the condensed phase. We report the realization of TR-XAS with a temporal resolution in the low femtosecond range by developing a tabletop high-harmonic source reaching up to 350 electron volts, thus partially covering the spectral region of 280 to 530 electron volts, where water is transmissive. We used this source to follow previously unexamined light-induced chemical reactions in the lowest electronic states of isolated CF 4 + and SF 6 + molecules in the gas phase. By probing element-specific core-to-valence transitions at the carbon K-edge or the sulfur L-edges, we characterized their reaction paths and observed the effect of symmetry breaking through the splitting of absorption bands and Rydberg-valence mixing induced by the geometry changes.

Near-band-edge optical responses of solution-processed organic–inorganic hybrid perovskite CH3NH3PbI3 on mesoporous TiO2 electrodes

Abstract: We studied the near-band-edge optical responses of solution-processed CH3NH3PbI3 on mesoporous TiO2 electrodes, which is utilized in mesoscopic heterojunction solar cells. Photoluminescence (PL) and PL excitation spectra peaks appear at 1.60 and 1.64 eV, respectively. The transient absorption spectrum shows a negative peak at 1.61 eV owing to photobleaching at the band-gap energy, indicating a direct band-gap semiconductor. On the basis of the temperature-dependent PL and diffuse reflectance spectra, we clarified that the absorption tail at room temperature is explained in terms of an Urbach tail and consistently determined the band-gap energy to be ~1.61 eV at room temperature.