Zur Konzentrationsabhängigkeit der Elektronenspin-Relaxationszeiten von Diphenyl-Picryl-Hydrazyl in fester Phase

The influence of exchange and dipol interaction on the EPR-relaxation timesT ₁ andT ₂ of DPPH has been measured in theX-band between 295 and 2°K. The spinconcentration has been varied between 1.5·10²¹ spins/cm³ (single crystals) and 1.5·10¹⁸ spins/cm³ (solid solution in polystyrene). The EPR absorption was saturated stationarily. This gave the productT ₁ T ₂ from the saturation curve and the timeT ₂ from saturation broadening of the absorption spectrum.     

Singular unitary representations and indefinite harmonic theory

Square-integrable harmonic spaces are defined and studied in a homogeneous indefinite metric setting. In the process, Dolbeault cohomologies are unitarized, and singlar unitary representations are obtained and studied.     

Orientation of anthracene molecules in naphthalene single crystals

The orientation of anthracene in naphthalene matrix has been determined by EPR of the triplet state of the guest molecule. It differs from the host molecule orientation mainly by a rotation of 25° about the z axis.     

Efficient methods for configuration interaction calculations

Advanced techniques are developed to provide efficient economic treatment of the large scale eigenvalue problem posed when configuration interaction is carried out on SCF basis sets of moderate size. When the characteristic properties of the hamiltonian matrix are examined in light of the type of solution required, partitioning of the configuration space is shown to result in an expansion of the problem about a limited core of states, where the small but cumulative interactions of vast regions of the remaining space are reduced to the form of an effective potential. With proper selection of the core, the evaluation of this potential can be readily and accurately truncated to a level involving minimum expenditure in time and effort. In particular only diagonal elements and a strip of the full CI matrix are required to achieve an accuracy of 1 – 5 kcal/mole with complete treatment for configuration spaces of order tens of thousands. In addition, a close look at current theory on the generation of matrix elements between spin symmetry adapted configurations leads to simplified expressions where the matrix elements are derived in the form of a weighted sum of molecular integrals in which the weighting coefficients represent the integrated value of the wavefunctions over spin coordinates. For typical cases of low multiplicity and limited numbers of open shells the list of unique parameters needed to generate all weights are shown to be readily stored as a program library. Actual times for matrix element generation are believed to be an order of magnitude faster than current techniques. Practical demonstration of the accuracy and efficiency of the method is provided by calculations on formaldehyde, water, and ethylene.     

Inequivalence Magnetique Due a la Presence d'un Atome de Phosphore Asymetrique ou Pseudo-Asymetrique

In phosphinous esters of general formula R? PH(O)OR', the asymmetric phosphorus atom induces magnetic non-equivalence in geminal protons and methyl groups. When alkoxy groups also possess an asymmetric carbon, the presence of the two possible diastereoisomers in equal amounts is proven by ³¹P and ¹H NMR. ³¹P NMR reveals that the phosphorus atom in phosphonous esters R? P(O·C₄H₉-s)₂ of racemic sec. butyl alcohol, is a centre of pseudo-asymmetry.     

Inclusive production in K+d reactions at 4.6 GeV/c

The investigations presented here are based on the data from a K⁺d experiment at 4.6 GeV/c performed with the 2 m bubble chamber at CERN. The topological K⁺d cross sections are determined. The integrated (semi-) inclusive single-particle cross sections for the production of π^?, K⁰ and Λ as well as (semi-)inclusive x- and p_T² distributions are measured and discussed.     

Optische Rotationsdispersion und Circulardichroismus bei Jod-Polysaccharid-Komplexen

Zusammenfassung Die wäßrigen Lösungen der Jodkomplexe von Stärke, verschiedenen Amylosen und Amylopektinen zeigen im Bereich der betreffenden Absorptionsmaxima einen induzierten positiven Cotton-Effekt. Die Drehwerte hängen in der gleichen Weise vom Jod-Amylose-Verhältnis ab wie die Extinktionen bei 660 und 445 m. Die Drehwerte einiger Jod-Polysaccharid-Komplexe nehmen mit der Zeit stark zu, obwohl die Extinktion konstant bleibt. Maßnahmen, durch welche die Struktur der Jod-Einschlußverbindung verändert wird (Erwärmung, Zusatz von Salzen, Lösungsmitteln, Harnstoff, Netzmitteln) haben einen starken Einfluß auf den induzierten Cotton-Effekt.

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Summary Aqueous solutions of iodine complexes with starch, different samples of amylose or amylopectin show an induced positive Cotton effect in the region of the absorption maximum. The rotatory power and the extinction at 660 and 445 m depends upon iodine amylose ratio. The optical of some complexes increases with time, whereas the absorption remains constant. Experimental conditions which change the structure of the channel complexe (heating, addition of salts, solvents, urea or detergents) influence the induced Cotton effect.

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Mit 8 Abbildungen in 9 Einzeldarstellungen und 1 Tabelle

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2. Mitt. J. macromol. Sci. Chem.A2 im Druck; 1. Mitt.R. Wolf undR. C. Schulz, Tetrahedron Letters1967, 1799.

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Vortrag anläßlich der 23. Arbeitstagung der Kolloid-Gesellschaft in Bad Oeynhausen 27. 10. 1967.

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Auszug aus der Dissertation vonH. Mayerhöfer, Mainz 1967, D. 77.     

Zur Ermittlung von Diffusionskoeffizienten in Festkörpern aus Sorptionsdaten

Zusammenfassung Für die Ermittlung von Diffusionskoeffizienten in Festkörpern aus Sorptionsdaten wurden die in der Literatur angeführten Näherungslösungen des zweitenFickschen Diffusionsgesetzes hinsichtlich ihrer Genauigkeit und ihrer Gültigkeitsbereiche untersucht. Dabei konnten zwei weitere Näherungslösungen mit größerer Genauigkeit abgeleitet werden. Zur Berechnung der Diffusionskoeffizienten wurde der ZeitparameterDt/r ² als Funktion vom Umsetzungsgrad mit einer relativen Genauigkeit von 0,001 (auch im Falle der Interpolation) tabelliert. Weiterhin werden einige graphische Verfahren zur Bestimmung des Diffusionskoeffizienten vorgeschlagen und deren Anwendungsmöglichkeiten diskutiert.

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Summary In order to determine the diffusivities in solids from sorption data, the approximation solutions of the secondFick's law as cited in literature have been investigated with regard to their accuracy and validity range. Two new approximation solutions showing a greater accuracy have been derived. With a view to compute the diffusivities, the time parameterDt/r ² has been tabulated as a function of the fractional attaintment of equilibrium, with a relative precision of 0.001 (also in the case of interpolation). Furthermore some graphic procedures for the determination of the diffusivities are proposed and their applicabilities are discussed.

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Mit 8 Abbildungen und 7 Tabellen