Search results for "Absorption"
showing 10 items of 2701 documents
Spectroscopic characterization of non-covalent CuPc-GO system. Experiment and theory
2019
Abstract In this study we report on UV-vis, IR and Raman studies of non-covalent copper phthalocyanine (CuPc) – flake graphene oxide (GO) complex in water and in the solid phase. Experimental results were supported by molecular modeling of structure, electronic and vibrational parameters for free CuPc and its 1 : 1 complexes with water, benzene, phenol, neutral and deprotonated benzoic acid. HOMO-LUMO gaps for these complexes were calculated and compared with data derived from the absorption edge of Q-band in the recorded UV-vis spectra for free CuPc and its adduct with GO in water. Small but non-negligible changes in position of spectral bands observed as result of CuPc interaction with GO…
Structural fluctuations in glass-forming liquids: Mössbauer spectroscopy on iron in glycerol.
1991
M\"ossbauer absorption spectra of $^{57}\mathrm{Fe}^{2+}$ dissolved in a glycerol-water mixture have been measured over a wide temperature range (80--275 K). In the supercooled liquid state the shapes of the spectra depend strongly on temperature. The M\"ossbauer spectra can be fit with jump diffusion with a Cole-Davidson distribution of fluctuation times. The results are in agreement with those obtained from dielectric and ultrasonic volume relaxations, proving that the \ensuremath{\alpha} relaxation of viscous liquids is responsible for the line broadening of the spectra. From the temperature dependence of the integrated area of the M\"ossbauer spectrum a second dynamic process is inferre…
The Optical And Epr Spectra of Fe(2+) and Fe(3+) Ions in the Blood of the Chernobyl Clean-Up Worker
2007
Electron paramagnetic resonance (EPR) and optical absorption studies of blood were provided for the group of Chernobyl’s NPP accident clean-up workers examined in the Center of Occupational and Radiological medicine of P.Stradins Clinical hospital of Medical Academy of Latvia. The EPR spectra for blood have been studied at low temperature. It is shown that in blood the ion Fe3+ of methemaglobin is in low-spin state with g = 2.3 and in the high spin state with g=6. We observed the additional absorption bands 500 nm (shoulder) and 630 nm in absorption spectra of blood of Chernobyl clean-up worker who has erythrocytosis.
Electrothermal Feedback and Absorption-Induced Open-Circuit-Voltage Turnover in Solar Cells
2018
A solar panel gets hot as it works up on the roof, yet photoinduced self-heating is often ignored when characterizing lab-sized samples. The authors present their understanding of the turnover effect in measurements of open-circuit voltage versus light intensity (Suns-${V}_{O\phantom{\rule{0}{0ex}}C}$ curves), which is identified as a unique feature of all semiconductor-based solar cells. This effect is explained in terms of electrothermal feedback arising when the incident irradiation heats up the device. The authors' model fully explains the experimental data, and allows one to determine key device parameters such as the ideality factor and the band gap from a single measurement.
Gd 3+ -doped sol-gel silica glass for remote ionizing radiation dosimetry
2019
Gadolinium-doped silica glass was prepared, using the sol-gel route, for ionizing radiation dosimetry applications. Such a glassy rod was drawn to a cane at a temperature of 2000 °C. The structural and optical properties of the obtained material were studied using Raman, optical absorption, and photoluminescence spectroscopies. Thereafter, a small piece of this Gd-doped scintillating cane was spliced to a transport passive optical fiber, allowing the remote monitoring of the X-ray dose rate through a radioluminescence (RL) signal. The sample exhibited a linear RL intensity response versus the dose rate from 125 µGy(SiO2)/s up to 12.25 Gy/s. These results confirm the potentialities of this m…
Structural and Optical Properties of Novel Surfactant Coated TiO2Ag Based Nanoparticles
2010
Stable dispersions of surfactant-coated TiO2–Ag based nanoparticles in apolar medium have been prepared by performing sequentially the hydrolysis of titanium(IV) isopropoxide and the reduction of Ag? in the confined space of sodium bis(2-ethylhexyl)sulfosuccinate (NaAOT) reverse micelles. Depending on the sequence length, this novel procedure allowed the synthesis of semiconductor–metal nanoparticles, nominally indicated as TiO2/Ag, TiO2/Ag/TiO2, and TiO2/Ag/TiO2/ Ag, stabilized by a monolayer of oriented surfactant molecules. The structural characterization of these nanoparticles has been performed by High Resolution Transmission Electron Microscopy (HR-TEM), while optical properties were …
Spectroscopic studies of Cr3+ ions in natural single crystal of magnesium aluminate spinel MgAl2O4
2021
Abstract The natural spinel crystal MgAl2O4 containing the Cr3+ ions was studied experimentally and theoretically in this paper. The absorption and emission spectra at room and low temperatures were recorded. The experimental spectroscopic results were aided with the crystal field calculations, which returned the energy level schemes of the Cr3+ ions at the Al sites with the local D3d symmetry. Effects of the trigonal crystal field were clearly seen in the calculated results, which were compared with the experimental spectra to yield a good agreement between both data sets.
Optical absorption and electron paramagnetic resonance of theEα′center in amorphous silicon dioxide
2008
We report a combined study by optical absorption (OA) and electron paramagnetic resonance (EPR) spectroscopy on the E{sub {alpha}}{sup '} point defect in amorphous silicon dioxide (a-SiO{sub 2}). This defect has been studied in {beta}-ray irradiated and thermally treated oxygen-deficient a-SiO{sub 2} materials. Our results have pointed out that the E{sub {alpha}}{sup '} center is responsible for an OA Gaussian band peaked at {approx}5.8 eV and having a full width at half maximum of {approx}0.6 eV. The estimated oscillator strength of the related electronic transition is {approx}0.14. Furthermore, we have found that this OA band is quite similar to that of the E{sub {gamma}}{sup '} center in…
Laser densification of organic coating: Effects of laser wavelength, operating parameters and substrate properties
2012
International audience; Mechanical bonding and interface behaviour play a key role for any materials deposited on different substrates. Usually, a post-spray heat treatment is required to improve the coating morphology and to enhance mechanical properties of thermal-sprayed polymeric coating. The effects of YAG, CO2 and diode laser radiations on as-sprayed PEEK coating deposited on stainless steel and aluminum substrates were investigated. The results revealed a good coating densification and interface behavior. A correlation between coating and substrate absorption coefficients, their thermophysical properties and laser operating parameters was shown. Besides, the finite element modeling b…
Anisotropic optical response of GaN and AlN nanowires.
2012
We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp(3), that includes the spin-orbit interaction. The passivation of the dangling bonds at the free surfaces is also studied, together with the effects on the electronic structure of the nanowire. For both GaN and AlN nanowires, we have found a remarkable anisotropy of the optical absorption when the light-polarization changes, showing in the case of GaN a dependence on the nanowire size.