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901.
The structures of mass selected silver cluster cations Ag19 +, Ag38 +, Ag55 +, Ag59 +, Ag75 +, and Ag79 + have been probed at a temperature of 100 K by trapped ion electron diffraction. The structure assignment is carried out by comparison of the experimental scattering intensity with theoretical scattering functions of calculated candidate structures obtained by density functional theory. For the cluster sizes studied the resulting experimental data are invariably best described by structures based on the icosahedral motif, while closed packed structures can be ruled out. 相似文献
902.
Heike Traub Markus W?lle Joachim Koch Ulrich Panne Ralf Matschat Heinrich Kipphardt Detlef Günther 《Analytical and bioanalytical chemistry》2009,395(5):1471-1480
Solution-doped metal powder pellets as well as aspirated liquids were used as calibration samples to analyze pure copper and
zinc certified reference materials (CRMs) by femtosecond laser ablation ICP-MS. It was demonstrated that calibration by copper
pellets resulted in relative deviations up to 20%, whereas fs-LA-ICP-MS among copper-based CRMs led to inaccuracies in the
same range unless nominal mass fractions were chosen to be <3 mg/kg. Calibration by zinc pellets generally provided better
accuracy. Depending on the analyte considered, deviations below 10% were obtained even for mass fractions close to the limit
of quantification. Our data, therefore, indicate solution-doped metal powder pellets to be suitable as calibration samples
for fs-LA-ICP-MS of metals. Furthermore, the utilization of liquid standards for calibration was found to result in stronger
deviations of up to 50% for both copper and zinc samples which, in addition, turned out to be dependent on the plasma conditions.
相似文献
903.
Jašíková L Hanikýřová E Schröder D Roithová J 《Journal of mass spectrometry : JMS》2012,47(4):460-465
Metal-oxide cations are models of catalyst mediating the C-H bond activation of organic substrates. One of the most powerful reagents suggested in the gas phase is based on CuO(+) . Here, we describe the activation of the aromatic C-H bonds of phenanthroline in its complex with CuO(+) . The reaction sequence starts with a hydrogen atom abstraction by the oxygen atom from the 2-position of the phenanthroline ring, followed by OH migration to the ring. Using infrared multiphoton spectroscopy, it is shown that the reaction can be energetically facilitated by additional coordination of a water ligand to the copper ion. As the reaction is intramolecular, a spectroscopic characterization of the product is mandatory in order to unambiguously address the reaction mechanism. 相似文献
904.
Erick M. Larramendi Z-B Karla Gutiérrez Osvaldo de Melo Ulrike Woggon Detlef Schikora Klaus Lischka 《Journal of Crystal Growth》2010,312(11):1807-1812
The use of a selenium–tellurium (SeTe) mixed source in the isothermal close space sublimation growth of CdSe epilayers is considered. The epitaxial growth was performed in flowing helium by sequential exposures of the substrate to vapors of the mixed SeTe source and elemental cadmium at temperatures within 350–410 °C. In spite of the mixed source (proposed to decrease the partial pressure of Se), tellurium incorporation was small and CdSexTe(1−x) (x∼0.98) epilayers were obtained. X-ray diffraction reciprocal space mapping shows the existence of hexagonal inclusions mainly on the (1 1 1) facets of the cubic phase. Material deposition on areas of the graphite crucible exposed to the sources, contamination of the Cd source and large growth rates suggest the existence of a selenium transport process via graphite. This transport might be the result of the combination of selenium deposition on graphite with a subsequent activated desorption of selenium under cadmium exposure. It affects Cd source purity and growth kinetic bringing on a modification of the usual atomic layer deposition regimen; however, a reproducible growth rate of the epilayers was obtained. 相似文献
905.
In order to simulate elastoplasticity within metal forming processes different approaches towards numerical implementation have been realized. Nevertheless, most of them or consider only the quasistatic case or use distinct time discretization schemes for the balance and the evolution equations. In the following, the effects of latter will be outlined on the basis of a numerical example exploiting a conventional ansatz towards finite elastoplasticity. This access should serve as a motivation for identifying why it is still important to investigate the implementation of elastoplastic phenomena beyond the well established methods. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
906.
We introduce a recently developed class of SolidState NMR experiments for the investigation of slow dynamic processes in organic solids. These 1D-MAS exchange experiments do not require selective isotopic labeling and can be performed with standard solid-state NMR hardware. The data are easy to analyze and provide selective information about the correlation times as well as about the topology (jump angles etc.) of dynamic processes in different sub-units of the molecules. We present data for Poly(n-butylmethacrylate), PBMA, between the glass transition temperature Tg and the αβ splitting temperature, in order to demonstrate the advantages of these 1D-MAS methods. 相似文献
907.
Detlef Schroeder Helmut Schwarz Matthias Wulf Heinrich Sievers Peter Jutzi Markus Reiher 《ChemInform》2000,31(11):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
908.
Xiaofeng Shi Jun Ma Ronger Zheng Chunyan Wang Heinz‐Detlef Kronfeldt 《Journal of Raman spectroscopy : JRS》2012,43(10):1354-1359
To detect trace‐level polycyclic aromatic hydrocarbons, some investigations of an improved self‐assembly method are carried out using gold colloid films for the preparation of the surface‐enhanced Raman scattering (SERS)‐active substrate. Extinction spectra and scanning electron microscopy images reveal that controllable surface plasmonic metal substrates can be obtained by increasing the temperature of (3‐aminopropyl)trimethoxysilane solution up to 64.5 °C. The SERS‐active substrates have a high enhancement factor, and they can be both easily prepared and reproducible. With the use of these substrates, different concentrations of pyrene and anthracene in aqueous solutions were detected by SERS. A further enhancement can be supported by shifted excitation Raman difference spectroscopy. Raman signals of pyrene and anthracene adsorbed on gold colloid substrates up to limits of detection at 5 and 1 nmol/l, respectively, can be obtained. The quantitative analysis shows the possibility of in situ detection of polycyclic aromatic hydrocarbons while such gold colloid film serves as a SERS‐active substrate. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
909.
Phillip Jackson Martin Diefenbach Ragampeta Srinivas Detlef Schroeder Helmut Schwarz 《ChemInform》2000,31(28):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
910.
Enno Lork Ruediger Mews Detlef Viets Paul G. Watson Tobias Borrmann Ashwani Vij Jerry A. Boatz Karl O. Christe 《ChemInform》2001,32(24):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献