Volume 38, Issue 7

Realizing that the internal structure of nucleons undergoes appreciable changes through embedding into nuclear matter the finite nucleus is considered from the outset as a correlated system of quarks. As an appropriate approximation scheme we introduce an extended bag model, i.e. a bag with nuclear radius containing all 3n quarks of the n-nucleon system. As the direct interaction we choose a SU (3)-invariant generalized pairing force which is supposed to contain the major effects of the more general term. As a result of the calculations containing a.o. a rigorous diagonalization of the total Hamiltonian, the characteristic properties of the conventional (nuclear) shell structure are reproduced: The spin orbit splitting appears now as a property of the relativistic single quark states, and the independent nucleon states are represented by correlated 3-quark-clusters. In addition, the nuclear radius law follows directly from a normal value of the vacuum pressure.

By chemical fixation of Kr in zeolite 5 A adequate samples can be obtained to determine the capture cross section of reactions such as 84 Kr (n, γ) 85 Kr m and 86 Kr (n, γ) 87 Kr. The employed zeolite loading was of the order 52-66 [cm 3 STP Kr/g zeolite]. The capture cross section of the reaction 84 Kr(n, γ) 85 Kr m was determined at thermal and 25 keV neutron energy. The value obtained at 25 keV is of relevance to the stellar nucleosynthesis of heavy elements.

A Markovian model of crack growth was presented in the first part of the paper. The present Part II presents a model for the case of random load, in order to obtain the probability distribution of the resulting crack size. A general model and the particular cases of a uniformly distributed stress intensity factor and mechanical work, are presented. This model separates the factors producing the crack growth in a homogeneous material from those considered in the Weibull model for nonhomogeneous materials.

The use of electron spin resonance in the study of the different steps in the impregnation process of hydrated Cu(NO 3 ) 2 onto silica gels with pore size of 20, 50 and 100 nm is described. The desolvation step with concomitant beginning of the salt decomposition step occurred at ~100 °C in silica with pores of 50 and 100 nm while a temperature higher than 200 °C were necessary for 20 nm pores. In the range 300 to 500 °C the decomposition step was completed and the adsorption of Cu(II) on ≡ SiO - surface sites started. Well-defined localization was completed after heating at 650 °C. The bond features of the surface adsorbed Cu(II) species are also described.

The method of Unrestricted Harmonie Balance (UHB) is a generally applicable procedure to determine the Fourier coefficients and constants of motion (frequency, velocity) of non-linear periodic phenomena in time and space and was outlined and applied to various problems in chemistry in preceding papers. Here the truncation error is investigated by comparing the UHB results for various truncation harmonics N with the rigorous analytical solution for the Kepler problem which is one of the rare examples of an exactly solvable non-linear problem.

Highly resolved emission spectra of Cr 3+ doped Trisacetylacetonatoaluminum(III) have been measured at various temperatures. By comparison with absorption spectra of dilute crystals the three most intense peaks have been assigned to the same molecular zero phonon transition according to three inequivalent Cr 3+ sites in the low temperature phase of the host crystal. The usually unobserved ground state splitting has been resolved (1.0 cm -1 ) in emission spectra at T = 1.9 K. Band assignments are confirmed by ligand Field calculations using complete trigonal perturbation matrices including spin-orbit coupling. From the obtained parameters K = 725 cm -1 and K′ = - 600 cm -1 the trigonal distortion of the chromium complex in the Al-crystal is determined. This indicates that the phase transition of the host crystal leads to rotations of rigid molecules while the molecular geometry remains.

The infrared spectrum of monoisotopic H 3 74 GeI has been investigated with a resolution of 0.04 cm -1 in the region of ν 6 and 2ν 6 . Rotational analyses (σ(J, K)~7 · 10 -3 cm -1 ) of ν 6 , 546.117(3), 2ν 6 ± 2 , 1094.731(4), and 2ν 6 0 , 1091.530(4) cm -1 , have been performed, and vibrational and rotational parameters of the apparently unperturbed υ 6 = 1 and 2 states have been obtained. Q branches of hot bands with ν 3 and ν 6 as lower states have been detected, and the anharmonicity constants X 36 , X 66 and g 66 have been determined. The simultaneous analysis of ν 6 ± 1 , 2ν 6 ± 2 and 2ν 6 ± 2 - ν 6 ± 1 provides an improved A 0 value.

The intermediate products A, B, C, D, E and V of the UV initiated solid state polymerization in single crystals of 2,4 hexadiynylene bis (p-toluene sulfonate), particulary their kinetics, have been studied by time resolved optical absorption spectroscopy in the temperature range between 180 and 300 K. The description by a simple kinetic model states that A to E react in a direct sequence by monomer addition, which is thermally activated. The activation energies range from 0.25 to 0.30 eV per monomer. At 300 K the reaction rate constants are of the order of 10 6 s -1 . - Product V is interpreted as a superposition of several long chain oligomers with reactive carbene chain ends. The reaction V → Polymer is thermally activated with an activation energy of 0,4 eV per monomer. - The fluorescence spectrum of the monomer crystal has been measured for the first time by use of a fast detection system. It is discussed with respect to its significance for the polymerization initiating step. - Deuterium isotope effects on the polymer absorption energy and on reaction kinetics are reported.

Specific volume and ultrasonic velocity measurements have been carried out on the liquid crystal N-(p-n-hexyloxybenzylidene)-p-n-butylaniline in the isotropic, nematic, smectic A, smectic B and smectic G phases. The variation of the specific volume with temperature shows that the corresponding transitions are of first order. Thermal expansion coefficients have been calculated for all the mesophases. The ultrasonic velocity variation with temperature confirms the transitions.

The molecular geometry of pentafluorobenzene sulphonyl chloride is characterized by the following bond lengths (r g ) and bond angles from an electron diffraction study: C-F 132.6 ± 0.3 pm, C-C 13971 ± 0.7 pm, S=O 141.5 ± 0.3 pm, S-Cl 202.7 ± 0.5 pm, C-S 179.8 ± 0.6 pm. C-S-Cl 104.8 ± 0.8°, C-S=O 108.2 ± 0.6°, O = S=O 123.6 ±1.0°, Cl-S=O 105.3 ±0.2°. The molecular model is asymmetric; the benzene ring is rotated by 61.8 ± 2.2° relative to the plane containing the S-Cl bond and bisecting the O = S = O angle. The benzene ring is not distorted considerably.

21 hyperfine multiplets, up to J = 12, have been measured for thionyl chloride ( 32 S 16 O 35 Cl 2 ), by means of microwave spectroscopy in the region 18.0 -26.5 GHz. Nuclear quadrupole coupling constants along the principal axes of inertia were determined to be χ aa = - 25.004 ± 0.040 MHz, χ bb = -0.009 ± 0.025 MHz and χ cc = 25.013 ± 0.031 MHz. Also, coupling constants along the S-Cl bond axis (z axis) and two axes perpendicular to this have been calculated to be χ xx = 65.93 MHz, /χ yy = 30.36 MHz and χ zz = -96.30 MHz. These values have been compared with those of other workers and with those of other related molecules. Information about the electronic distribution in the S-Cl bond has been obtained from the values of these constants, and the results have been discussed.

The reaction path of malononitrile dimerization, the intermediates and the tautomerism of the final product have been investigated by the MNDO method. The results are in good agreement with experimental data. The mechanism has a barrier height of about 88 kJ/mol and involves an intermediate which passes to the most stable tautomer through intermolecular proton transfer.

The effect of terminal polar and nonpolar substituents on the thermodynamic stability of the mesophase is discussed. Mesomeric as well as steric effects influence the packing of the molecules and consequently the clearing point. It is necessary to consider the effect of substituents in connection with the nature of the rigid core. The influence of molecular association and conformational equilibria on the stability of the mesophase is described. Isolated electron densities lead to repulsions between neighbouring molecules, thus destabilizing the mesophase and the layered structure if present.

The complexity of dynamical behavior possible in nonlinear (for example, electronic) systems depends only on the number of state variables involved. Single-variable dissipative dynamical systems (like the single-transistor flip-flop) can only possess point attractors. Two-variable systems (like an LC-oscillator) can possess a one-dimensional attractor (limit cycle). Three-variable systems admit two even more complicated types of behavior: a toroidal attractor (of doughnut shape) and a chaotic attractor (which looks like an infinitely often folded sheet). The latter is easier to obtain. In four variables, we analogously have the hyper-toroidal and the hyper-chaotic attractor, respectively; and so forth. In every higher-dimensional case, all of the lower forms are also possible as well as “mixed cases” (like a combined hypertoroidal and chaotic motion, for example). Ten simple ordinary differential equations, most of them easy to implement electronically, are presented to illustrate the hierarchical tree. A second tree, in which one more dimension is needed for every type, is called the weak hierarchy because the chaotic regimes contained cannot be detected physically and numerically. The relationship between the two hierarchies is posed as an open question. It may be approached empirically - using electronic systems, for example.

Spectroscopic studies of the dark space ahead of a detached shock wave caused by a blunt body were made in a partially ionized argon flow. From emission measurements, spatially resolved population densities of states 5p[3/2], 5p[5/2] and 4p[3/2] were determined at 20 stations in the flow, for both cases when the blunt body is placed in the flow and when it is withdrawn. The result shows that the population densities of the above mentioned states ahead of the shock wave are reduced when the body is placed in the flow. A prediction was obtained by assuming a steady state population for all levels higher than level 4 s. In the prediction the measured electron temperatures and densities were employed to determine collisional transition probabilities. From a comparison of the experiment with the prediction, it is considered that the dark space is caused by the elevation in the electron temperature ahead of the shock wave.

A series of chemiluminescence (CL) investigations of rare earth ions in redox reactions has been initiated. The study of oxidation reactions of Eu 2+ - uncomplexed and complexed by ethylenediaminetetraacetic acid (EDTA) -with H 2 O 2 has revealed a distinct CL of Eu 3+ with two-phasic kinetics, controlled by pH and the concentration of H 2 O 2 .

In the systems investigated only the compounds AsAlCl 8 and AsGaCl 8 g are found. Raman spectra were recorded for the solid and molten compounds and for mixtures with excess ASCl 3 + CL 2 and AlCl 3 and GaCl 3 , respectively. The observed frequencies are assigned to tetrahedral AsCl 4 + , AlCl 4 - and GaCl 4 - units. Melting of AsCl 4 AlCl 4 and AsCl 4 GaCl 4 causes a decomposition into AsCl 3 , Cl 2 and AlCl 3 and GaCl 3 , respectively.