Zur Magnetochemie des zweiwertigen Silbers Neue Fluoroargentate(II): Cs2AgF4, Rb2AgF4 und K2AgF4

Magnetochemistry of Divalent Silver. New Fluoroargentates(II): Cs₂AgF₄, Rb₂AgF₄, and K₂AgF₄ Hitherto unknown blue compounds Rb₂AgF₄ and Cs₂AgF₄ are prepared. Guinier patterns show, that Cs₂AgF₄ cristallise in the K₂NiF₄ structure (a = 4.58₁, c = 14.19₂ Å). The structure of the Rb-compound is still unknown. The magnetic behaviour of K₂AgF₄, Rb₂AgF₄, and Cs₂AgF₄ is discussed.     

The analysis of inorganic siliceous materials by atomic absorption spectrophotometry and the hydrofluoric acid decomposition technique : Part I. the analysis of silicate rocks

The analysis of various inorganic siliceous materials of geological and industrial interest is discussed. The methods proposed are based on decomposition of a single sample by hydrofluoric acid and determination by atomic absorption spectrophotometry of up to 10 constituents. General procedures are described, and details are given for the determination of silicon, aluminium, total iron, magnesium, calcium, sodium, potassium, titanium and manganese in silicate rocks. Analytical data are given for the analysis of reference rocks G-2 and W-1.     

Magnetic circular dichroism of theA andB bands in KI:Ga+, KI:In+, and KI:Sn2+

Magnetic circular dichroism (MCD) of theA- andB-absorption band region has been obtained at 4.2 K and 50 kG in KI:Ga⁺, KI:In⁺, and KI:Sn²⁺. The MCD spectra indicate the complex nature of these bands more clearly than the absorption spectra themselves do. TheA-band MCD consists in all cases of a positive and a negative part reflecting the structure of the absorption band. TheB-band MCD shows three peaks, two positive peaks at 4.34 and 4.41₅ eV (4.09 and 4.17₅ eV) and a negative peak at 4.38 eV (4.12₅ eV) in KI:Ga⁺ (KI:In⁺). TheB-band in KI:Sn²⁺ consists of a shoulder (b ₀) at 3.76 eV and a main band which has at least 5 sub-peaks (b ₁~b ₅) at 3.82₁, 3.84₁, 3.86₁, 3.88₀, and 3.89₅ eV; each of the subpeaks (b ₁~b ₅) gives a derivative-like MCD.The MCD shape functionf() for the transitiona _1g ² a _1g t _1u has been obtained for one set of parameter values by using the classical Franck-Condon approximation and the Monte Carlo integration method. The result can explain the observed salient features of theB- as well asA-band MCD's, indicating the validity of the Franck-Condon approximation and the interaction mode coordinates.     

Die Fluoreszenz von Z1-Zentren in KCl

Zeitschrift für Physik A Hadrons and nuclei - Detailed measurements on the absorption, emission and excitation spectra of Z1 centers in KCl doped with Ca, Sr or Ba are reported. Beyond the...     

Optical and EPR investigations of a new hydrogen center in potassium chloride

In KCl interstitially diffusing neutral hydrogen atoms (H _i ⁰ ) can be trapped near substitutional Li⁺ ions. The new center possesses a characteristic absorption band at 250nm, at the long wavelength side of the knownH _i ⁰ absorption band (235nm). EPR measurements reveal, that the hydrogen atoms are closely connected to the Li⁺ ions at a cation lattice site forming (LiH)⁺ molecules. Below 70K hydrogen and lithium occupy a fixed relative position to each other in a (111) crystal direction: the hydrogen shows a superhyperfine interaction to three equivalent Cl^– neighboring ions. Above 70K the hydrogen exhibits a superhyperfine interaction to six equivalent chlorine neighbors, interpreted by a rapid reorientational motion of the (LiH)⁺ molecule within the cation vacancy. The high temperature interaction parameters can be explained as the time average of the low temperature values. A qualitative explanation of the optical absorption of the (LiH)⁺ center is given.     

Zur Magnetochemie der Fluoroargentate(II): Messungen an Ba[AgF4], Sr[AgF4], Ba2AgF6 sowie K[AgF3] und Cs[AgF3]

Magnetochemistry of Fluoroargentates(II): Investigation of Ba[AgF₄], Sr[AgF₄], Ba₂AgF₆, K[AgF₃], and Cs[AgF₃] Ba[AgF₄] (Θ = -4 K, μ = 1.9₂ μ_B), isostructural with K[BrF₄] with planar [AgF₄] groups, fullfil the Curie-Weiss-law, also Ba₂AgF₆ (Θ = 4 K, Θ = 1.8₅ μ_B) which is related with the structure of Ba₂CuF₆. The variante of perovskite-type K[AgF₃] (orthorhombic) and Cs[AgF₃] (tetragonal perovscite) show collective magnetic interactions (T_N = 80 K, KAgF₃, and 50 K, CsAgF₃) and show a behaviour like AgF₂ (T_N160 K) correspondingly to the magnetic dilution. Above T_N paramagnetism is nearly independend of tempearture.     

Sports drug testing using immuno-MS: clinical study comprising administration of human chorionic gonadotropin to males

The applicability of a mass spectrometry (MS)-based method for determination of various forms of human chorionic gonadotropin (hCG) in doping analysis was demonstrated. A clinical study involving the hCG-containing pharmaceuticals Pregnyl and Ovitrelle was carried out, comprising a single injection of one pharmaceutical per participant to a total of 24 healthy male voluntaries. Hereafter, serum and urine samples were collected over a period of 14 days. The analysis of the samples using immuno-MS demonstrated elimination profiles of intact hCG for both pharmaceuticals, with last day of detection following administration at day 7 in serum, and at day 10 in urine, at limit of detections as defined by the World Anti-Doping Agency. Furthermore, the method allowed detection and differentiation of the various forms of hCG known to be present in serum and urine as a function of metabolism. For both pharmaceuticals, only the intact hCG was detected in serum, whereas in urine the injection of Pregnyl as hCG source (containing urinary hCG, i.e., most hCG variants) was shown to generate a more complex hCG variant pattern compared to Ovitrelle (contains only intact hCG). By detecting hCG using this MS-based approach in doping analysis, strong analytical evidence is provided minimizing the risk of false-positive and false-negative results.     

Color centers in the ionized and in the triplet state —Z 2 centers in calcium doped KCl crystals

Optical absorption measurements ofZ ₂ andZ ₂ ⁺ centers in KCl:Ca are combined with electron spin resonance experiments in order to reveal the electronic and atomistic structure of these centers.Z ₂ ⁺ centers are alignable in the crystal by polarized optical irradiation at suitable temperatures. From orientedZ ₂ ⁺ centers equally orientedZ ₂ centers can be produced, both types of centers showing a (100) axial symmetry. ConcerningZ ₂ this is also confirmed by ESR measurements on their triplet state produced by optical excitation. Polarized excitations allow a determination of the ratio of oscillator strengths for transitions parallel and perpendicular to the center axis using the variations in ESR line intensities. ForZ ₂ f /f =1.6 is found in this way; decomposition of the dichroism ofZ ₂ ⁺ centers gives for this speciesf /f =1.8. It is shown that theZ ₂(Ca) center is a molecule made up of a Ca⁺⁺ ion and an anion vacancy in (100) nearest neighborhood, sharing two electrons with antiparallel spins in the ground state. Both, withZ ₂ andZ ₂ ⁺ , the absorption bands at lowest energies are best explained bys—d charge transfer transitions.     

Sum of squares manifolds: The expressibility of the Laplace-Beltrami operator on pseudo-Riemannian manifolds as a sum of squares of vector fields

In this paper, we investigate under what circumstances the Laplace-Beltrami operator on a pseudo-Riemannian manifold can be written as a sum of squares of vector fields, as is naturally the case in Euclidean space.

We show that such an expression exists globally on one-dimensional manifolds and can be found at least locally on any analytic pseudo-Riemannian manifold of dimension greater than two. For two-dimensional manifolds this is possible if and only if the manifold is flat.

These results are achieved by formulating the problem as an exterior differential system and applying the Cartan-Kähler theorem to it.