Niob, Tantal

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Faktorklassen in Graphen

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Über Gruppengeschwindigkeit,Energiestromdichte und Energiedichte in der Röntgen- bzw. Lichtoptik der Kristalle

Studying the propagation of X-rays (or visible light) in perfect crystals, the wellknown expression for the group velocity vector can be used and interpreted in terms of the dispersion (or index) surface. The group velocity vector, being normal to the dispersion surface in the point representing the appropriate wavefield, is shown to be proportional to the average of the Poynting vector observable macroscopically. The factor occuring in this relation is the averaged energy density of the electroagnetic field, which differs from the usual expression by a term proportional ??/?ν as a consequence of the frequency dependence assumed for the dielectric tensor ?.     

Azotometrische Bestimmung von Penicillin

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Die hochaufgel?sten (100 MHz-) KMR-Spektren von Phenyllithium und Di-phenylmagnesium

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Experimental and theoretical study of the electron-phonon scattering rate in potassium

Limiting-point radio-frequency size effect measurements have been performed in potassium to measure the anisotropy and magnitude of the electron-phonon scattering rate. The anisotropy is too small to be resolved by the method, and is estimated to be less than 10 per cent at low temperatures. Theoretical calculations confirm the small anisotropy, but yield a rate at least 40 per cent larger than that observed.     

Effect of molecular weight on the refractive increment of polyethylene and n-alkanes

As in the case with other polymers previously reported, the values of the refractive index increment dn/dc of polyethylene and the n-alkanes change with molecular weight. Most of the variation may be understood by examination of the role of density in the Lorentz-Lorenz mixing equation for specific refractivity, R₁₂ = p₁R₁ + P₂R₂ used to calculate dn/dc. It may also be shown that as the absolute refractive index difference between solute and solvent becomes smaller, dn/dc becomes more sensitive to density change of the solute.     

Determination of nuclear multipole relaxation times by measurements of statistically perturbed angular correlations

It is pointed out that phenomena of nuclear multipole relaxation can also be studied by the observation of perturbed angular correlations. The corresponding formulae are derived and compared with the results of other authors. A compilation of experimental results is presented.