Electronic spectra

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  • This book consists of a collection of review chapters that summarize the recent progress in the areas of metal and semiconductor nanosized crystals (nanocrystals). The interest in the optical properties of nanoparticles dates back to Faraday’s experiments on nanoscale gold. In these experiments, Faraday noticed the remarkable dependence of the color of gold particles on their size. The size dependence of the optical spectra of semiconductor nanocrystals was first discovered much later (in the 1980s) by Ekimov and coworkers in experiments on semiconductor-doped glasses.

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  • Deviations from Beer’s law (i.e. deviations from the linearity of absorbance vs. concentration): – Intermolecular interactions at higher concentrations – Chemical reactions (species having different spectra) – Peak width/polychromatic radiation Beer’s law is only strictly valid with single-frequency radiation Not significant if the bandwidth of the monochromator is less than 1/10 of the half-width of the absorption peak at halfheight.

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  •  UV-Visible spectra can be interpreted to help determine molecular structure, but this is presently confined to the analysis of electron behavior in known compounds.  Information from other techniques (NMR, MS, IR) is usually far more useful for structural analysis  However, UV-Vis evidence should not be ignored!

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  • The Series ‘Topics in Molecular Organization and Engineering’ was initiated by the Symposium ‘Molecules in Physics, Chemistry, and Biology’, which was held in Paris in 1986. Appropriately dedicated to Professor Raymond Daudel, the symposium was both broad in its scope and penetrating in its detail. The sections of the symposium were: 1. The Concept of a Molecule; 2. Statics and Dynamics of Isolated Molecules; 3. Molecular Interactions, Aggregates and Materials; 4. Molecules in the Biological Sciences, and 5. Molecules in Neurobiology and So- ciobiology.

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  • To examine the role of the distal His42 residue in the catalytic mechanism of pea cytosolic ascorbate peroxidase, two site-directed variants were prepared in which His42 was replaced with alanine (H42A) or glutamic acid (H42E). Electronic spectra of the ferric derivatives of H42A and H42E (pH 7.0, l ¼ 0.10 M, 25.0 °C) revealed wavelength maxima [kmax (nm): 397, 509, % 540sh, 644 (H42A); 404, 516, % 538sh, 639 (H42E)] consistent with a predominantly fiveco-ordinate high-spin iron. The specific activity of H42E for oxidation of L-ascorbate (8.2 ± 0.

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  • Chapter 14 introduce to ethers, epoxides, and sulfides. After completing this chapter, students will be able to: Draw and name ethers and heterocyclic ethers, including epoxides; explain the trends in their boiling points, solubilities, and solvent properties; determine the structures of ethers from their spectra, and explain their characteristic absorptions and fragmentations;...

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  • The characteristics lines in X-ray spectra result from electronic transitions between inner atomic orbitals. The X-ray spectra for most heavy elements are much simpler than the UV/Vis spectra observed in ICP-OES, for example. (Only a few lines!!!) Big difference between X-ray and UVVis: The radiation is ionizing, and doesn’t just excite electrons to higher levels. Moseley’s law: Predicts the basic relationship of atom number and the frequency of the characteristic lines

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  • It is difficult to overemphasize the importance of magnetic resonance techniques in chemistry. Experimental spectra can usually be successfully interpreted empirically, but more difficult cases require a prediction based on the electronic structure. In the last 25 years the calculation of magnetic resonance parameters from first principles has become a powerful research tool that can significantly enhance the utility of magnetic resonance techniques when empirical interpretations are insufficient.

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  • Gardelis et al. Nanoscale Research Letters 2011, 6:227 http://www.nanoscalereslett.

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  • The powders of Mg(Al1-xEux)2O4 have been synthesized by sol-gel method. Optical properties of the material were investigated. The nature of lines in luminescence spectra is related to the electron transitions of Eu3+ ions corresponding to different sites in the lattice. The influence of Eu concentration on optical spectra was studied.

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  • Conventional and saturation transfer electron paramagnetic resonance spectroscopy (EPR and ST EPR) was used to study the orientation of probe molecules in muscle fibers in different intermediate states of the ATP hydrolysis cycle. A separate procedure was used to obtain ST EPR spectra with precise phase settings even in the case of samples with low spectral intensity. Fibers prepared from rabbit psoas muscle were labeled with isothiocyanate spin labels at the reactive thiol sites of the catalytic domain of myosin....

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  • La0.9Ce0.1Mn0.5Cu0.5O3 was prepared by the combustion method using polyvinyl alcohol (PVA) and corresponding metal nitrates. Samples were characterized by thermogravimetric and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), FT-IR spectra, transmission electron microscopy (TEM) and BET (Brunaure-Emmet-Teller) measurements. The results show that perovskite phase is formed at 600o C. Sample synthesized under optimal condition has nanostructure with large specific area.

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  • The hole closing reported in this letter is certainly not caused by deposition of carbon-rich material by the electron beam, a common phenomenon in electron microscopy. The observation that large pores expand is in direct contradiction with potential contamination growth. Secondly, electron-energy-loss spectra (EELS) locally obtained on the material that filled a nanopore clearly show the presence of silicon and oxygen,but the absence of any carbon (detection limit was less than 2%).

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