Volume 49, Issue 7-8

The nonrelativistic constituent quark model for excited baryon states in the version proposed by Isgur and Karl is extended toward higher energies by including all states containing up to three oscillator excitation quanta. At high energies baryon resonances with spins up to 9/2 become accessible. At all energies and in particular for lower spins strong configuration mixing is obtained. Model predictions are compared to the empirical resonance energies derived in the Karlsruhe-Helsinki pion nucleon phase shift analysis. A search is made for parameter sets that apply simultaneously to the positive parity and the negative parity states. Numerical results are presented and discussed in relation to experimental data and to other theoretical works.

In this article a new method for solving the multi-dimensional Schrödinger-equation for electrons and nuclei will be discussed. It is shown by application of integral transformations and by use of space-filling curves how the multi-dimensional Schrödinger-equation can be replaced by an one­ dimensional integral equation. Furthermore the problems of accuracy arising due to the use of this approximative treatment are pointed out. The presented method can be stated without the Born-Oppenheimer approximation and the application of determinants for fitting the wave function is discussed in a new one-dimensional point of view.

We show how computer algebra can be used to find time dependent first integrals of dissipative dynamical systems. Extended Lorenz models are studied as examples.

A definition is proposed for the number of χ electrons x involved in a three-center bond, based upon the corresponding two-center bond indices. The number of electrons is fractionary, ranging from about 1 to somewhat more than 4 in the systems considered here. It is seen that the sign of the three-center index does not depend on χ.

This work is based on published analytical data of 69 pieces of Chinese greenware bodies from seven famous wares: Yue, Longquan, Southern Song Guan, Ru, Jun, Yaozhou, and Ge. It is possible to do provenance studies of these wares by the application of principal component analysis using major and minor chemical constituents (Si0 2 , Al 2 O 3 , Fe 2 O 3 , CaO, MgO, K 2 O , Na 2 O , and TiO 2 ). The results show that not only are northern and southern greenwares completely distinct in the raw materials used, but in addition the southern greenwares are reasonably well segreated into groups belonging to Yue ware, Longquan ware (white body), Longquan ware (black body) and Southern Song Guan ware. Our analysis also confirms the production of Ge ware in the Longquan area.

The Γ 1 (A 1g ) → Γ 1 ( 3 T 1g ) luminescence spectra of mixed Cs 2 [OsCl n Br 6-n ], n = 1-5, have been measured between 15 800 and 17 000 cm -1 at 10 K. As a host lattice Cs 2 [TeCl 6 ] has been doped with purely isolated chloro-bromo-osmates(IV), including the geometrical isomers with n = 2, 3, 4. The assignments of the electronic transitions and their extensive vibronic structure are discussed.

The structure factor of amorphous germanium was determined using 120 kV electrons, an Ω-filter for the elimination of inelastically scattered electrons and a correction procedure for multiple scattering. The structure factor thus obtained is in good accordance to that obtained with X-rays and neutrons, respectively.

The formation of neutral bimolecular clusters of unsubstituted nucleobases and mononucleosides in the gas phase has been studied by IR laser desorption of the neutral molecules into a supersonic beam expansion. The complementary nucleobase pairs adenine-thymine and cytosine-guanine of D N A have been found to be formed in preference to non complementary base pairs. Association constants for the formation of the dimers of free nucleobases and nucleosides in the gas phase are calculated from the experimental results. A strong influence due to side groups affecting the dimer formation of the nucleobases is shown.

The short range structure of molten NaHSO 4 (I) and KHSO 4 (II) was estimated by X-ray diffraction. The polyatomic anion, HSO 4 - , in both molten salts was found to have a distorted tetrahedral structure in which the bond lengths of S-O and S-OH were 1.45 Å and 1.53 Å in (I) and 1.46 Å and 1.56 Å in (II), respectively. The coordination number of the Na + or K + around the HSO 4 - was evaluated to be about unity. The semi-empirical molecular orbital calculations by the MNDO-MOPAC method were applied to the determination of the intraionic structure of the H S 0 4 and the bond lengths of S-O and S -OH were computed to be 1.528 Å and 1.666 Å, respectively, supporting qualitatively that the HSO 4 - forms a rather distorted tetrahedron.

The basic expressions governing derivative enumeration are given and a sufficient condition proposed which applies to isonumeric compounds.

Single photon ionization of C 60 in 2,2-dimethylpropane (neopentane, NP), 2,2,4,4-tetramethylpentane (TMP), 2,2-dimethylbutane (neohexane, DMB), and 2,2,4-trimethylpentane (isooctane, iso-OCT), and of C 70 in TMP was studied by photoconductivity measurement. Threshold energies of the photoconductivity were determined. From these results, the polarization energies and the ionic radii of the cations were obtained by application of Born's formula. The ionic radii turned out to be smaller than the van der Waals radii of the molecules.

An analytical pair potential function for the Cl - -NH 2 OH interaction energy surface has been constructed based on basis set superposition error corrected ECP/DZP ab initio calculations. The potential has been tested by Monte Carlo simulation of a solution of one chloride ion in liquid hydroxylamine at 32 °C, leading to the conclusion that under these conditions Cl-forms a solvation shell of eight solvent molecules, coordinated via OH hydrogens.

The vibrational and rotational characteristics of the ground bands of even-even nuclei with 150 ≤ A ≤ 166 (2 < R 4 < 3) are studied. The spectra of these nuclei (with band crossing angular momentum I C ≥ 12) are analyzed with a cubic polynomial in I. The considered nuclei ( 150 Sm, 152 Gd, 154-156 Dy, 156 Er, 158-160-162 Yb and 162,164, 166 Hf) lie in the central region between the Z = 50 and Z = 82 major shell closures and span the spherical to the well deformed region. The gradual shape transition from a soft spherical vibrator to a deformed rotor from 150 Sm to 166 Hf is thus made explicitly apparent from the g-band spectrum analysis in terms of the vibrational, rotational and softness coefficients. The transition at N = 88-90 for the vibrational-rotational ratios and for the kinematic moments of inertia are reproduced.

The short range structure of molten ErCl 3 at 1053 K was investigated by X-ray diffraction. The nearest neighbour distance of Er 3+ -Cl - and the coordination number of Cl - around Er 3+ were estimated to be 2.63 Å and 5.8 Å, respectively, and the Er 3+ -Er 3+ and Cl - -Cl - distances 4.05 Å and 3.75 Å, respectively. The ratio of the anion-anion pair distance to the cation-anion pair distance (r -- /r+ - ) was, therefore, 1.43, being close to 1.41, characteristic of octahedral geometry. These results indicate that ErCl 6 3- -octahedra exist in molten ErCl 3 . Probably Er2Clio and a small amount of Er2Cl 11 5- ions are formed according to the geometrical calculations of bond lengths and bond angles.

A modification of the Karplus equation is put forward, containing for mutually independent structural terms and four adjustable parameters. Among the new factors introduced in this modifi­cation are the distance between protons and Muallay's group electronegativity, used in the evalua­tion of the α-substituent effect. The new equation reproduces experimental NMR vicinal coupling constants with a standard deviation of about 0.6 Hz.

A new class of fractal structures displaying a structural transition on growing is studied by considering the morphology selection mechanism under the biharmonic field V̄ 2 (V̄ 2 u) = 0 as recently proposed by the authors [Phys. Rev. E 47, 476 (1993)]. By relating the growth probability for each site to the local ("potential") field as (V̄ 2 u) n , the effects of the surrounding medium and of geometrical constraints for the seed particles are numerically calculated and discussed. A theoretical estimation of the transition point is given anew by solving the biharmonic equation with the boundary conditions used in simulations.

The effect of temperature (from 296 to 423 K) upon the absorption and fluorescence of l-phenyl-4-diphenylthiophosphinyl butadiene (PDPB) and of the direct irradiation on the absorbance were investigated in poly(vinyl alcohol) film. It was found that for PDPB in PVA film the transition from cis to trans configuration is only possible as a result of thermal isomerization due to the softening of PVA polymer, whereas photoisomerization results in both cis-to-trans and trans-to-cis transitions. Similar as with 1,4-diphenyl-1,3-butadiene in PVA, the luminescence is due to two, trans-trans and cis-trans, PDPB conformers.

The masses of pseudoscalar mesons are approximately proportional to quadratic powers of integers.