Predissociation spectroscopy of the argon-solvated H5O2+ "zundel" cation in the 1000-1900 cm(-1) region

Predissociation spectra of the H5O2+.Ar(1,2) cluster ions are reported in the 1000-1900 cm(-1) region. The weakly bound argon atoms enable investigation of the complex in a linear action mode, and the resulting spectra are much simpler than those reported previously in this region [Asmis et al., Science 299, 1375 (2003) and Fridgen et al., J. Phys. Chem. A 108, 9008 (2004)], which were obtained using infrared multiphoton dissociation of the bare complex. The observed spectrum consists of two relatively narrow bands at 1080 and 1770 cm(-1) that are likely due to excitation of the shared proton and intramolecular bending vibrations of the two water molecules, respectively. The narrow linewidths and relatively small (60 cm(-1)) perturbation introduced by the addition of a second argon atom indicate that the basic "zundel" character of the H5O2+ ion survives upon complexation.     

Chemical reactions in the atomization of molybdenum in graphite furnace atomic absorption spectrometry

Summary Chemical reactions in the atomization of molybdenum in graphite furnace atomic absorption spectrometry have been studied using graphite platforms for atomization along with X-ray diffraction analysis. When Mo [as an aqueous solution of (NH₄)₂MoO₄] is heated in a graphite furnace, three molybdenum oxides: [MoO_2(s), MoO_3(s) and Mo₄O_11(s)], are formed at relatively low temperatures (<1,500 K). When Mo is atomized from a pyrolytic graphite surface, the charring curve of Mo shows a dip in absorbance in the temperature range 1,200–1,800 K. Hence, a charring temperature <1,200 K should be used for quantitative determination of Mo when a pyrolytically coated tube or a platform made of pyrolytic graphite is used. Mo_(s), MoC_(s) and Mo₂C_(s) have been found on both the pyrolytic and the regular graphite surface after the charring step is completed. Formation of Mo_(g) by direct sublimation of Mo_(s) and by dissociation of MoC_(g) are all thermodynamically favourable reactions at the temperature considered.

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Chemische Reaktionen bei der Atomisierung von Molybdän in der Graphitofen-AAS

Zusammenfassung Die chemischen Reaktionen bei der Atomisierung von Molybdän wurden mit Hilfe von GraphitPlattformen zusammen mit der Röntgen-Diffraktionsanalyse untersucht. Bei der Erhitzung von Molybdän [als wäßrige (NH₄)₂MoO₄-Lösung] im Graphitofen werden drei Molybdänoxide (MoO_2(s), MoO_3(s) und Mo₄O_11(s)) bei relativ niedrigen Temperaturen (<1 500 K) gebildet. Wenn Molybdän von einer pyrolytischen Graphitoberfiäche atomisiert wird, zeigt die Veraschungskurve eine Absenkung der Extinktion im Bereich von 1200 bis 1800 K. Deshalb sollte bei Verwendung eines mit pyrolytischem Graphit überzogenen Rohres oder einer entsprechenden Plattform für quantitative Molybdänbestimmungen eine Veraschungstemperatur von <1 200 K benutzt werden. Nach der Veraschungsstufe wurden sowohl auf der pyrolytischen als auch auf der normalen Graphitoberfläche Mo_(s), MoC_(s) und Mo₂C_(s) gefunden. Bildung von Mo_(g) durch direkte Sublimation von Mo_(s) und durch Dissoziation von MoC_(g) sind thermodynamisch günstige Reaktionen bei der betreffenden Temperatur.

     

Numerical Kähler-Einstein Metric on the Third del Pezzo

The third del Pezzo surface admits a unique Kähler-Einstein metric, which is not known in closed form. The manifold’s toric structure reduces the Einstein equation to a single Monge-Ampère equation in two real dimensions. We numerically solve this nonlinear PDE using three different algorithms, and describe the resulting metric. The first two algorithms involve simulation of Ricci flow, in complex and symplectic coordinates respectively. The third algorithm involves turning the PDE into an optimization problem on a certain space of metrics, which are symplectic analogues of the “algebraic” metrics used in numerical work on Calabi-Yau manifolds. Our algorithms should be applicable to general toric manifolds. Using our metric, we compute various geometric quantities of interest, including Laplacian eigenvalues and a harmonic (1,1)-form. The metric and (1,1)-form can be used to construct a Klebanov-Tseytlin-like supergravity solution.