Search results for "Spectroscopy"
showing 10 items of 10293 documents
Up-conversion processes in NaLaF4:Er3+
2009
abstract Structural and spectroscopic investigation of NaLaF 4 :Er 3+ material at different doping concentrations ispresented. X-ray diffraction patterns, up-conversion luminescence spectra and decay curves for 2 H 9/2 ? 4 I 15/2 , 4 S 3/2 ? 4 I 15/2 and 4 F 9/2 ? 4 I 15/2 optical transitions in the material are shown and possibleexcitation routes are discussed. Raman spectrum for the undoped material is presented and the effectivephonon energy of the material is estimated. Based on the obtained results application of rare-earth dopedNaLaF 4 in the field of up-conversion phosphors is evaluated. 2009 Elsevier B.V. All rights reserved. 1. IntroductionFor many years rare-earth (RE) doped materi…
Über gemischte Gruppe 14—Gruppe 14-Bindungen
1991
Abstract p-Tol6PbSn has been synthesized by reaction of p-Tol3PbLi with p-Tol3SnI in THF/ether (1:2) at −78°C. The crystal structures of p-Tol4Pb (I 4 ) and of p-Tol6Sn2, p-Tol6PbSn and p-Tol6Pb2 have been determined. The three dinuclear compounds crystallize not strickly isomorphous. They exhibit the same space group (R 3 and rather similar unit cell dimensions. Yet according to the solvent of crystallization, two types with differing atomic position parameters can be distinguished (“homoeotypism with differences of parameters” in the definition of Laves). In both types, the individual molecules have a chiral C3-symmetric conformation and the non-chiral unit cell encloses both enantiomers.…
Electric field induced alignment-orientation conversion in diatomic molecules: analysis and observation for NaK
1999
This article reports the observation of the molecular fluorescence circularity under irradiation with linearly polarised light. This alignment-orientation conversion phenomenon arises as a result of partial transformation from alignment of the ensemble of 1 P state molecular angular momenta into their orientation under the effect of non-linear dc Stark effect. Circularity rate up to 0.12 was observed in D 1 P! X 1 S fluorescence of 23 Na 39 K molecules in agreement with the theoretically predicted value.
5-Alkenyl-1,2,3-thiadiazole
1986
Es wird die Herstellung der Titelverbindungen 5 durch Bromierung-Dehydrobromierung entsprechender 5-Alkyl-1,2,3-thiadiazole 3, ihre spektroskopische Charakterisierung und ihre Umsetzung mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion (6) zu 7, 8 beschrieben. 5-Alkenyl-1,2,3-thiadiazoles A method of preparation for the title compounds 5, by bromination-dehydrobromination of the corresponding 5-alkyl-1,2,3-thiadiazoles 3, their spectroscopical characterization, and the reaction of 5 with 4-phenyl-4H-1,2,4-triazole-3,5-dione (6) with formation of 7, 8 is described.
Crystal and molecular structure of anhydrous betaine, (CH3)3NCH2CO2
1999
Abstract 1–Carboxy–N,N,N–trimethylmethanamanium inner salt or anhydrous betaine, (CH3)3NCH2CO2, FW=117.15 gmol −1 , crystallizes in the orthorhombic space group Pnma with a=14.544(2) A , b=6.859(3) A , c=6.131(1) A , V=611.7(3) A 3 , Z=4, D x =1.27 Mgm −3 , λ (MoK α )=0.71073 A , μ =0.091 mm −1 . The structure was resolved by direct methods and refined by least-square calculations to R=0.038 for 531 reflections. Observed changes in bond angles imply that there is a repulsion between nitrogen and oxygen. The melting point (measured at onset) is 570 K. FTIR spectra of anhydrous betaine and monohydrate were recorded. Clear differences were found between the two compounds based on infrared (i.r…
Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)am…
2006
Abstract Bis[dibenzyldimethylammonium]CuBr4, bis[dibenzyldimethylammonium]CuCl4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX4·0.5 CH3CN (X=Br or Cl) in monoclinic space group P21/n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX4 (X=Br or Cl) crystallized without solvent molecules. The formed…
Properties of new low melting point quaternary ammonium salts with bis(trifluoromethanesulfonyl)imide anion
2010
Eight new monocationic quaternary ammonium (QA) salts with the bis(trifluoromethanesulfonyl)imide (TFSI) anion were prepared by metathesis using our previously reported QA halides as precursors. New salts were characterized both in liquid and solid state using 1 H and 13 C NMR techniques, mass spectroscopy and elemental analysis together with X-ray diffraction and thermoanalytical methods. In addition, residual water content, viscosity and conductivity measurements were made for three of the roomtemperature ionic liquids (RTILs). The crystal structures of three compounds were determined by X-ray single crystal diffraction. Powder diffraction was used to study the crystallinity of the solid …
Studies in organic mass spectrometry. Part 25. Benzyl ion formation in chemical ionisation (methane or isobutane) of someortho-alkylhetero-substitute…
2000
The behaviour of some ortho-alkylhetero-substituted diphenylcarbinols, including deuterium labelled derivatives, under chemical ionisation (methane or isobutane) conditions has been investigated. It has been determined that ortho-alkylhetero diphenylmethyl cations formed by water elimination from the protonated molecule undergo consecutive rearrangements which afford benzyl (or tropylium) ions previously observed for ortho-substituted diphenylcarbenium ions generated by electron ionisation. This reaction also occurs under low-energy collision conditions. Copyright © 2000 John Wiley & Sons, Ltd.
Synthesis and in vitro evaluation of galanthamine derivatives for examination of nicotinic acetylcholine receptor system
2001
ISunmrary: The syntheses and radioactive labeling of several galanthamine derivatives, 6-O-demethyl-6-O-fluoroethylgalanthamine, 10-N-demethyl-lO-Nfluoroethylgalanthamine and N-methylgalanthaminium are reported. First ill vitro evaluations were carried out to determine their properties as allosterically potentiating ligands of nicotinic receptors. N-methylgalanthaminium was found to be a promising candidate for further investigations. The most commonly applied therapeutic approach to balance nicotinic cholinergic deficits in Alzheimer’s disease (AD) patients is the administration of acetylcholinesterase inhibitors (AChE-I) although they have been proven to be of limited therapeutic value [ …