Search results for "Absorption"
showing 10 items of 2701 documents
X-ray absorption spectroscopic study of trivalent and tetravalent actinides in solution at varying pH values
2009
Abstract We perform X-ray absorption spectroscopy (XAS) investigations to monitor the stabilization of redox sensitive trivalent and tetravalent actinide ions in solution at acidic conditions in a pH range from 0 to 3 after treatment with holding reductants, hydroxylamine hydrochloride (NH2OHHCl) and Rongalite (sodium hydroxymethanesulfinate, CH3NaO3S). X-ray absorption near edge structure (XANES) measurements clearly demonstrate the stability of the actinide species for several hours under the given experimental conditions. Hence, structural parameters can be accurately derived by extended X-ray absorption fine structure (EXAFS) investigations. The coordination structure of oxygen atoms be…
The Hot Bands of Methane between 5 and 10 μm
1996
Experimental line intensities of 1727 transitions arising from nine hot bands in the pentad-dyad system of methane are fitted to first and second order using the effective dipole moment expansion in the polyad scheme. The observed bands are nu3 - nu2, nu3 - nu4, nu1 - nu2, nu1 - nu4, 2nu4 - nu4, nu2 + nu4 - nu2, nu2 + nu4 - nu4, 2nu2 - nu2, and 2nu2 - nu4, and the intensities are obtained from long-path spectra recorded with the Fourier transform spectrometer located at Kitt Peak National Observatory. For the second order model, some of the 27 intensity parameters are not linearly independent, and so two methods (extrapolation and effective parameters) are proposed to model the intensities …
Red and Far-Red Fluorescence Emission Retrieval from Airborne High-Resolution Spectra Collected by the Hyplant-Fluo Sensor
2018
The contribution presents the development and testing of a fluorescence retrieval scheme based on the ESA's FLuorescence EXplorer mission concept. The algorithm employs on a coupled surface-atmosphere forward model at oxygen absorption bands: i) the atmospheric effect is computed by MODTRAN5; ii) the surface reflectance and fluorescence are modeled by means of the Spectral Fitting approach. The algorithm, previously tested on numerical simulations, was further implemented and optimized to process real observations collected by the FLEX airborne demonstrator HyPlant. The retrieval scheme has been tested on a number of flight lines collected in several locations, different ecosystems types, a…
First experiment with the NUSTAR/FAIR Decay Total Absorption γ-Ray Spectrometer (DTAS) at the IGISOL IV facility
2015
V. Guadilla et al. ; 4 págs.; 4 figs.; 1 tab.
Light absorption in silicon quantum dots embedded in silica
2009
The photon absorption in Si quantum dots (QDs) embedded in SiO2 has been systematically investigated by varying several parameters of the QD synthesis. Plasma-enhanced chemical vapor deposition (PECVD) or magnetron cosputtering (MS) have been used to deposit, upon quartz substrates, single layer, or multilayer structures of Si-rich- SiO2 (SRO) with different Si content (43-46 at. %). SRO samples have been annealed for 1 h in the 450-1250 °C range and characterized by optical absorption measurements, photoluminescence analysis, Rutherford backscattering spectrometry and x-ray Photoelectron Spectroscopy. After annealing up to 900 °C SRO films grown by MS show a higher absorption coefficient a…
The HITRAN2016 molecular spectroscopic database
2017
This paper describes the contents of the 2016 edition of the HITRAN molecular spectroscopic compilation. The new edition replaces the previous HITRAN edition of 2012 and its updates during the intervening years. The HITRAN molecular absorption compilation is composed of five major components: the traditional line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, infrared absorption cross-sections for molecules not yet amenable to representation in a line-by-line form, collision-induced absorption data, aerosol indices of refraction, and general tables such as partition sums that apply globally to the data. The new HITRAN is greatly extended in terms of …
Computational determination of the dominant triplet population mechanism in photoexcited benzophenone
2014
In benzophenone, intersystem crossing occurs efficiently between the S-1(n pi(star)) state and the T-1 state of dominant n pi(star) character, leading to excited triplet states after photoexcitation. The transition mechanism between S-1(n pi(star)) and T-1 is still a matter of debate, despite several experimental studies. Quantum mechanical calculations have been performed in order to assess the relative efficiencies of previously proposed mechanisms, in particular, the direct S-1 -> T-1 and indirect S-1 -> T-2(pi pi(star)) -> T-1 ones. Multiconfigurational wave function based methods are used to discuss the nature of the relevant states and also to determine minimum energy paths a…
Optical absorption of torus-shaped metal nanoparticles in the visible range
2007
Received 22 November 2007; published 19 December 2007We theoretically and experimentally investigated the optical response of a thin metal nanotorus in the visiblerange. The close formulas describing the extinction cross sections of a torus are obtained in the nonretardedapproximation. We demonstrate a good agreement between numerical simulations and experimental data. Ourfindings show that the main resonance is highly sensitive to the external medium and the geometrical param-eters of the particle.DOI: 10.1103/PhysRevB.76.245422 PACS number s : 78.67.Bf, 73.20.Mf, 78.20.Ci
Growth and characterisation of MnTe crystals
2001
We report on the low temperature growth of MnTe crystals by means of travelling solution methods. Two different processes are considered; a classical THM process using a low temperature presynthesised MnTe ingot, and a modified THM process, in which an increasing length of solvent zone collects the tellurium that was added to the stoichiometric charge to decrease the reaction temperature. Ingots from the two methods are analysed by means of scanning electron microscopy, X-ray diffractometry, resistivity, susceptibility and optical absorption measurements.
Resolvent estimates for the magnetic Schrödinger operator in dimensions ≥2
2020
It is well known that the resolvent of the free Schrödinger operator on weighted L2 spaces has norm decaying like λ−12 at energy λ . There are several works proving analogous high frequency estimates for magnetic Schrödinger operators, with large long or short range potentials, in dimensions n≥3 . We prove that the same estimates remain valid in all dimensions n≥2 . peerReviewed