NMR study of fluorine and proton motion in the ionic conductor NH4Sn2F5

The nuclear spin relaxation times of protons and fluorine atoms in the ionic conductor NH₄ Sn₂ F₅ show a particular temperature behaviour: they decrease as the temperature decreases below 200 K and have the same temperature and frequency dependences.Cross relaxation experiments show an important coupling between fluorine atoms and protons. NMR results as well as crystallographic and conductivity data on hydrogenated and deuterated compounds, allow to determine two dominant kinds of motion: at low temperature the reorientation of the ammonium ion is observed and above 250 K the diffusion of the fluorine atoms is responsible for the relaxation. In the high temperature range, the activation energies of the motion deduced from conductivity and NMR measurements are in good agreement.     

Caracterisation par analyse thermique differentielle des complexes metalliques fulviques et humiques

Journal of Thermal Analysis and Calorimetry - L'étude préliminaire de complexes artificiels de fer ou de calcium avec les acides fulviques et humiques permet d'interpréter...     

Caracterisation par analyse thermique differentielle des complexes metalliques fulviques et humiques

Journal of Thermal Analysis and Calorimetry - On a caracterisé par analyse thermique différentielle sous atmosphère d'oxygène des complexes humiques et fulviques...     

Anomeric effect of radicals

The glucosyl radical 1 is attacked predominately at the axial position. This can be explained by an anomeric effect that stabilizes σ-radical 5.     

Etude de quelques métastannates de métaux bivalents et de leur évolution sous l'action de la chaleur

Résumé L'étude de l'évolution des métastannates de Zn, Cd, Cu, Ni, Co, Mg et Ca sous l'action de la chaleur met en évidence des différences d'un stannate à l'autre. Les sels de cuivre et manganèse se dissocient totalement alors que ceux de cadmium, zinc, cobalt, magnésium et calcium se transforment en orthostannates qui sont identifiés par leur spectre d'absorption infrarouge.

---

Summary The study of the evolution of the metastannates of Zn, Cd, Cu, Ni, Co, Mg, and Ca under the action of heat reveals some differences from one stannate to the other. The salts of copper and manganese dissociate completely while those of cadmium, zinc, cobalt, magnesium and calcium are transformed into orthostannates which are identified by their infrared absorption spectra.

---

Zusammenfassung Die Bildung der Metastannate von Zn, Cd, Cu, Ni, Co, Mg und Ca beim Erhitzen zeigt Unterschiede zwischen den einzelnen Stannaten. Die Salze des Kupfers und des Mangans zersetzen sich vollständig, während sich die des Cadmiums, Zinks, Kobalts, Magnesiums und Calciums in Orthostannate umlagern, die an ihrem Infrarotabsorptionsspektrum zu erkennen sind.

     

GANIL有机金属离子束流的现状报告

Previous experiments with organo-metallic compounds like ferrocene,nickelocene and magnesocene showed that a pure spectrum must be obtained on the residual gas mass analyser before running successfully on the ion source.In collaboration with the chemistry department of the University of Caen,LCMT-ENSI Caen,the synthesis of these metallocene compounds has been studied to provide enriched isotopic compounds to GANIL’s users.The chemical transformation yields were 90%,80% and 43%,respectively.Vanadocene, chromocene,colbatocene and ruthenocene compounds have first been studied with a gas mass analyser and then successfully tested on the ECR 4M ion source at GANIL.Some 15eμA of ~(51)V~(11 ),20eμA of ~(52)Cr~(11 ), 22eμA of 59Co~(11 ),and 17eμA of ~(102)Ru~(11 ) were achieved.The comparison between the results obtained on the gas mass analyser and the ion beams provided by the source has allowed us to validate this method of determining whether or not an organo-metallic compound could be a candidate for running on our ECR ion source.As the ECR ion sources are tuned and used alternately on the GANIL injectors,the available time for the tests is rare,so this method could be an alternative for the validation of new compounds.     

An ab initio MO study on the thymine dimer and its radical cation

Ab initio SCF calculations with the 6-31G basis set for the thymine dimer (cys-syn form) and the thymine dimer radical cation are reported. The fusion of the thymine bases at the C5 and C6 positions involves the formation of a cyclobutane ring with puckering. The puckering causes a notable difference in the electronic structures of the two bases of the thymine dimer. The density of the HOMO orbital of the thymine dimer is localized on the O2, N1, and C6 atoms of both thymine rings, with the higher density on one of the rings. The HOMO orbital has a bonding character on the C6(SINGLEBOND)C6 bond. In the thymine dimer radical cation, the unpaired electron is localized mainly on the lengthened C6(SINGLEBOND)C6 bond with the higher density on one of the C6 atoms and to a lesser extent on the N1 atoms of both rings. © 1996 John Wiley & Sons, Inc.     

Epitaxial growth and characterization of InAs/GaSb and InAs/InAsSb type-II superlattices on GaSb substrates by metalorganic chemical vapor deposition for long wavelength infrared photodetectors

We report on the epitaxial growth and characterization of InAs/GaSb and InAs/InAsSb type-?? superlattices (T2SLs) on GaSb substrates by metalorganic chemical vapor deposition. For InAs/GaSb strained T2SLs, interfacial layers were introduced at the superlattice interfaces to compensate the tensile strain and hence to improve the overall material quality of the superlattice structures. The optimal morphology and low strain was achieved via a combined interfacial layer scheme with 1 monolayer (ML) InAsSb+1 ML InGaSb layers. In contrast, the InAs/InAsSb strain-balanced T2SLs allow for a relatively easy strain management and simple precursor flow switching scheme while maintaining device-quality materials. Surface root mean square roughness of 0.108 nm and a nearly zero net strain were obtained, with effective bandgaps of 147 and 94 meV determined for two sets of InAs/InAsSb strain-balanced T2SLs.     

The OH radical-H2O molecular interaction potential

The OH radical is one of the most important oxidants in the atmosphere due to its high reactivity. The study of hydrogen-bonded complexes of OH with the water molecules is a topic of significant current interest. In this work, we present the development of a new analytical functional form for the interaction potential between the rigid OH radical and H(2)O molecules. To do this we fit a selected functional form to a set of high level ab initio data. Since there is a low-lying excited state for the H(2)O.OH complex, the impact of the excited state on the chemical behavior of the OH radical can be very important. We perform a potential energy surface scan using the CCSD(T)/aug-cc-pVTZ level of electronic structure theory for both excited and ground states. To model the physics of the unpaired electron in the OH radical, we develop a tensor polarizability generalization of the Thole-type all-atom polarizable rigid potential for the OH radical, which effectively describes the interaction of OH with H(2)O for both ground and excited states. The stationary points of (H(2)O)(n)OH clusters were identified as a benchmark of the potential.