Band 35, Heft 1

Electron-proton and electron-deuteron scattering experiments in a wide four momentum range provide information about the structure of the proton and the neutron. The structure is a direct consequence of the hadronic interaction of the nucleon and reveals properties of the strong interaction. Absolute differential cross sections can be expressed in terms of electromagnetic form factors which lead to an understanding of the coupling mechanism between the electromagnetic field and the strongly interacting hadron. The structure can also be discussed in terms of charge densities, but this analysis is strongly restricted by recoil effects. The charge rms radius extracted from recent measurements is higher in the case of the proton than that derived from former fits. The higher value of the charge rms radius of the proton is in excellent agreement with the latest Lamb shift measurements.

The evaporation of the synthetic compounds CsAlSiO 4 and CsAlSi 5 O 12 was studied by high temperature mass spectrometry. The measurements were carried out under equilibrium conditions with Knudsen cells in the temperature ranges 1242 to 1567 K (CsAlSiO 4 ) and 1542 to 1803 K (CsAlSi 5 O 12 ). The obtained Cs partial pressures are given by the equations log p (Pa)=-18497/T(K)+11.85(CsAlSiO 4 )and log p (Pa)=-26 974/T(K)+14.6(CsAlSi 5 0 12 ). The probable uncertainty of the vapor pressures is ± 43%. The following enthalpies of sub­limation of Cs (g) were computed: ⊿ Sub H° 1405 (CsAlSiO 4 ) =353.6 ± 9.8 kJ mol -1 and ⊿ Sub H° 1673 (CsAlSi 5 O12) =516.3 ± 18 kJ mol -1 . The Cs partial pressures over CsAlSiO 4 , CsAlSi 5 O 12 and CsAlSi 2 O 6 (see part I of this work [1]) are discussed with respect to their consequences for the final storage of high level radioactive waste.

The molecular and crystal structures of dibrom maleic acid thioanhydride and diiod maleic acid thioanhydride have been determined by means of single-crystal X-ray intensities. The crystal structures are isomorphous and have the space group P4 1 2 1 2 (enantiomorphous with P4 3 2 1 2). The lattice constants are a = 7.543 Å, c = 12.155 Å (DBMTA) and a = 7.816 Å, c = 12.348 Å (DIMTA). The five-membered rings of the molecules are planar with maximum deviations of 0.003 Å (DBMTA) and 0.005 Å (DIMTA). Adjacent molecules are held together by van-der-Waals-forces.

A procedure for the automatic evaluation of ion-sensitive photographic plates used in spark source mass spectrography is described. Using an optical wedge microdensitometer the line-transmittance profiles are measured and stored. In a second step the transmittance profiles are converted into ion-intensity profiles, according to the equation of Franzen et al. [8], and inte-grated. The two methods, peak height and integrated intensities, are compared in terms of precison and accuracy.

Isotopic ratios measured with thermal ionisation mass-spectrometers are biased by fractionation effects. A sample must therefore be analyzed according to the same procedures as applied for the analysis of the standard reference material. A comparison of the behaviour of the sample with that of the standard can then be used as a criterion whether the analytical results are acceptable or not. In this way it is possible to obtain reproducibilities similar to those for elements where the fractionation can be determined by an internal standard. This procedure of controlled fractionation is demonstrated by means of the 88 Sr/ 86 Sr ratios measured on geological samples and the SRM 987 standard.

The unequilibrated hypersthene chondrite Yamato-74191 was studied mass spectrometrically for rare gases released at various temperatures. Cosmogenic gases dominate in He and Ne. The meteorite contains large amounts of trapped Ar, Kr and Xe, and radiogenic 40 Ar and 129 Xe. Cosmic-ray irradiation and K-Ar ages were determined. In addition to spallogenic components of Kr and Xe, isotopic excesses of 80 Kr, 82 Kr, 128 Xe and 126 Xe relative to AVCC-Kr and -Xe were found. The ratio of 80 Kr-excess to 82 Kr-excess is 2.66 after correction for spallogenic Kr. A correlation between 128 Xe/ 132 Xe and 129 Xe/ 132 Xe was found The 129 Xe/ 132 Xe ratio for trapped Xe in Yamato-74191 was determined as 1.12 ± 0.29 with the correlation plot. The excesses found in Yamato-74191 are best explained by epithermal neutron capture on Br and I, and by the 127 I (n, 2nβ) 126 Xe reaction. Using neutron-produced 80 Kr, the neutron slowing -down density was estimated to be 0.14 ± 0.03 cm -3 sec -1 . A minimum mass and a preatmospheric radius was estimated to be 470 kg and 32 cm, respectively.

Results are reported for the contents of He, Ne, and Ar of three different specimens from the Kirin H-chondrite which, with a recovered weight of about 4000 kg, is the largest known stone meteorite. The concentrations of spallogenic gases cover a range of more than a factor of two; bulk samples with ratios 3 He/ 21 Ne ≲ 2 and a FeNi nugget with 3 He/ 38 Ar = 8.8 ± 0.6 indicate strong diffusion losses of 3 He from the silicates and of tritium from the metal. - Radiogenic 4 He and 40 Ar have been affected by diffusion, too, resulting in discordant U/Th- 4 He- and 40 K- 40 Argas retention ages as well as distinctly different ages for different samples. Stepwise heating experiments show the main release of 4 He and 40 Ar to occur at around 800 °C and the difference in the gas contents to be due to differences in the low-temperature part of the gas release curve. - An attempt is made to account for the observed positive correlation between the concentrations of spallogenic and radiogenic noble gas nuclides. Either the diffusion losses of both have occured at the same time which requires a (quasi-)continuous loss due to a small perihelion distance or a catastrophic event late during the cosmic ray exposure history, but more than about 10 5 years before the fall of the meteorite. As an alternative model it is suggested that the Kirin meteoroid was hot upon the ejection from its parent body. As the subsequent cooling rate of the meteoroid is smallest in the interior the diffusion losses of radiogenic 4 He and 40 Ar will be largest where the production rate of the cosmogenic nuclides is smallest.

The concentrations and isotopic composition of noble gases have been determined in all ten stone meteorites recovered in Antarctica during 1976-1977 by a U.S.-Japanese expedition. From a comparison of spallogenic and radiogenic gas components it is concluded that the chondrites Mt. Baldr (a) and Mt. Baldr (b) belong to the same fall but that all other stone meteorites are individual finds.

The cosmic-ray produced rare gas nuclides and the isotopic composition of potassium have been measured in a sample from the iron meteorite Unter-Mässing. Unusually high concentrations of the rare gas nuclides have been found. Accordingly, an unusually high exposure age of ≈ 1400 Ma was determined by the 41 K/ 40 K-method. Unter-Mässing is a meteorite of the chemical group IIC. Thereby, it is the third one found among ≈ 80 meteorites heretofore dated which belongs to one of the sparsely populated side-groups or to no group at all, and at the same time exhibits an extraordinarily high exposure age (anomalous iron Deep Springs: ≈ 2300 Ma, IIIF-Clark County: ≈ 1400 Ma). The experimental data allow, by procedures developed recently, to estimate the pre-atmospheric size of the meteoroid to have been ≈ 2000 kg and the sample investigated to come from a shielding depth of ≈ 16 cm. According to this size estimation. Unter-Mässing cannot be a fragment broken off from the impact projectile of the Nordlinger Ries crater either in the atmosphere at high altitudes or at the explosive impact event.

The concentrations of Fe, Ni, Co, P, Cu, Ga, Ge, Mo, Ru, Rh, Pd, W, Ir and Pt in the phosphides and the metal of the coarse octahedrites Campo del Cielo, Canyon Diablo, Cranbourne and Sardis, the coarsest octahedrite São Julião de Moreira and the hexahedrites Braunau and Lombard have been determined by spark source mass spectrometry. Striking differences are observed of the element contents between bulk meteorite and the phosphides as well as between the different phosphide modifications schreibersite and rhabdite. Extreme values are a 20 fold depletion of Ga and a 40 times higher content of Pd in the phosphides. A particularly strong correlation between the noble metal element content and size of phosphide aggregates is observed; it is shown that this correlation is not an artifact of the sample preparation but that is must be real.

The Zaisho meteorite, a pallasite from Japan, is primarily composed of nickel-iron and olivine, and contains minor amounts of troilite, schreibersite, chromite and farringtonite. The olivine of this meteorite is Fa 18.6 in molar composition, and exhibits non-rounded morphology. About 17% of the olivines are kinked crystals. The formational temperature was estimated to be 1220 °C from the Mg-Fe 2+ distribution coefficient in the coexisting olivine-chromite pair.

The anisotropy of the probability distribution function for the unit vector joining two nearest neighbour atoms is characterized by tensorial order parameters. For cubic symmetry, the most relevant tensor is of rank 4. Starting from an ansatz for the dependence of the (specific) internal energy, volume and entropy; the entropy production is calculated which is caused by a temporial change of the 4-th rank anisotropy tensor. A constitutive law which guarantees that the entropy production is positive leads to a nonlinear relaxation equation. It shows the features typical for a dynamic Ginzburg-Landau theory. The linearized version of the relaxation equation contains an effective relaxation time and a correlation length which exhibit a temperature dependence typical for a mean field theory. For a special case where the anisotropy tensor can be characterized by a scalar order parameter, the nonlinear relaxation equation is studied in some detail. Its stationary and spatially homogeneous solutions are zero and nonzero values for the order parameter depending on whether the temperature T is larger or smaller than the transition temperature. The unordered phase corresponds to a liquid state, the ordered phase to a simple or body centered cubic crystal. The phase transition is of 1st order. There exist also metastable states.

The stability of internal modes, i.e. modes which leave the plasma boundary unperturbed, is discussed for magnetohydrostatic equilibria in circularly cylindrical symmetry. Stability analysis can be performed analytically by expansion near the magnetic axis. Marginal stability conditions relating the pressure gradient and the shear are determined.

The microsegregation behaviour of antimony in the faceted and non-faceted Czochralski silicon crystal growth was analyzed quantitatively. Using small melt heights and no rotation, dopant striations of various small spacings were eliminated. Interface demarcation and spreading resistance measurements were used for the segregation analysis. The dopant concentration and its fluctuation during the faceted growth were both higher than during non-faceted growth. On the other hand, fluctuations of the microscopic growth rate were about the same in magnitude and periodicity in the two growth regions.

A theoretical description of micellar dye solutions containing donors and acceptors is developed. It is proved experimentally that the luminescent characteristics of Water-Triton X-100 solutions of Coumarine 1 as a donor and Rhodamine 6G as an acceptor are consistent with the proposed theory. It is shown that the probability of energy transfer between dye molecules and the number of detergent molecules in a micelle may be obtained.

Proton spin-lattice relaxation rates have been measured at 30 MHz as a function of temperature for a large number of dimeric copper complexes with the ligands 8-hydroxyquinoline, pyridine-N-oxide, methyl and dimethyl pyridine-N-oxide, and quinoline-N-oxide. Two carboxylates and adducts of several complexes with various solvents have also been studied. In contrast to some compounds with a normal magnetic behaviour, for most complexes a temperature dependent relaxation has been observed which agrees well with the concept of a weak antiferromagnetic interaction between the two Cu 2+ ions. The singlet-triplet separations or exchange integrals have been determined.

The phase transition temperatures and enthalpies were determined by differential scanning calorimetry between room temperature and the isotropic liquid region for the lithium n.alkanoates from tridecanoate to eicosanoate. The number and nature of the phases involved were discussed in comparison with the literature data available for some of the homologues concerned. For diffe-rent kinds of transitions, the significant features of the plots AS vs. number of carbon atoms were put into evidence.

Raman spectra of some solid and molten PCl 5 -HgCl 2 mixtures (formation of 2 phases) have been recorded. In the system investigated the compounds (PCl 4 ) 2 HgCl 4 and (PCl 4 ) n (HgCl 3 ) n were found. The structure of (PCl 4 ) n (HgCl 3 ) n is polymeric likely as that of NH 4 HgCl 3 . In this case melting causes a fragmentation into smaller but still polynuclear units of varying chain length. The temperature dependency of the solubility of PCl 5 in the lower phase influences the existing equilibria.

The first neighbour model, FNM, used frequently for the description of hydration has been modified by dropping the assumption that the structure of the "free" solvent is identical with that of the pure solvent. The modified model, FNM2, reproduces the experimental X-ray structure functions of alkali chloride solutions quite well and enables the study of perturbed solvent-solvent interactions. The refined structural parameters reasonably indicate the dependence of the hydration of the alkali cations on their radius and concentration. The hydration of Cl - has been found to be almost independent of both concentration and the type of counter cation. The model assumes regular symmetry for the first neighbour coordination sphere, but the high rms deviations of the water-water distances within the shells of the aggregates indicate con-siderable individual asymmetries. A further modification of the FNM will be discussed in a following paper.

Co(trz) 2 (NCS) 2 has been investigated by means of magnetic susceptibility and magnetization measurements on single crystals in the temperature range from 1.1 - 300 K, heat capacity measure­ments from 1.5 - 90 K, neutron powder diffraction at 1.2 K and ESR measurements on the Co­doped Zn compound at 9 K. The compound appears to have two-dimensional structural and mag­netic properties. A transition to an antiferromagnetically ordered state takes place at T c = 5.71 (1) K. Susceptibility measurements along the three orthorhombic axes reveal a strongly anisotropic character. The b axis is found to be the preferred axis of antiferromagnetic alignment. The susceptibility data along b and the heat capacity results are in good agreement with the predictions for the quadratic layer, S=½, XY antiferromagnetic, with an intralayer exchange constant j/k= -5.0(1)K. Below T c the field dependent behaviour of the magnetization and the susceptibility along the a axis exhibits a transition at ~ 1 kOe. Hidden canting is found to be present. The magnetic structure can be described by four sublattices with the magnetic moments lying in the a-b plane along directions that are at an angle of 7° with the b axis.

The influence of α- and o-methyl substituents on the conformation of phenylcyclopropane is studied. Synthesis as well as low temperature PMR studies of the corresponding derivatives are carried out. The changes in the PMR spectra measured at room temperature and -100 °C are too small to count for the rotation barrier calculations. Fo 2,2-dichloro-1-phenyl-cyclopropane (8) ,2,2-dichloro-1-methyl-1-phenyl-cyclopropane (9) and 2,2-dichloro-1-o-tolyl-cyclopropane(10) the predicted most stable conformation is the near-bisected in which the aromatic ring is slightly twisted towards the CI atoms. For 2,2-dichloro-1-(2,6-dimethyl-phenyl)-cyclopropane (11) the planar conformation is predicted to be most stable. MINDO/3-FORCES calculations of the conformations and rotation barriers of similarly methylsubstituted vinyl-cyclopropanes, phenylcyclopropane and 2-cyclopropyl-pyridine are reported. It is found that introducing a methyl group to the a-position of the three membered ring or to the C 4 atom f the vinylgroup causes the deviation of the olefine plane from the bisected conformation by 30°. Similar deviations are expected for the α-and o-methyl-phenylcyclopropanes.

The UV absorption spectra of phenyl-cyclopropane(l), 267 nm, 1-methyl-1-phenyl-cyclopro-pane(2), 259 nm, o-tolyl-cyclopropane(3), 264 nm, m-tolyl-cyclopropane (4), 270 nm, and p-tolyl-cyclopropane(5), 280 nm are recorded in the gas phase, in methanol and in n-hexane. The hypsochromic shifts in the spectra of both 2 and 3 are explained in terms of a twisting of the phenylring out of the bisected conformation which causes an increase in the excitation energy. The spectra of 4 and 5, in which no steric factors are expected to twist the phenylring, show typical inductively caused bathochromic shifts. The vibronic structuring of all the absorption spectra are analyzed and found to include the frequencies 984, 964 and 1100 cm -1 that are attributed to the and the ν as vibrations of the ν̃s cyclopropyl ring in the excited state. The results of the analysis confirm a recent assumption of a strong participation of the ⊿ as Walsh MO of these Molecules in their electronic excitation processes.