Band 53, Heft 9

The N = 2 ← 1 rotational transition of the PH radical in its ground electronic (X 3 Σ - ) and vibrational states has been measured with the Cologne terahertz spectrometer in the frequency region between 920 and 1070 GHz. The PH radical was generated by immersing red phosphorus in a dc glow discharge of molecular hydrogen buffered with argon. Transition frequencies of the five J′ - J″ fine structure components together with the associated hyperfine structure patterns were precisely measured and analyzed to derive highly accurate molecular parameters, which are more extensive than those reported in the existing literature. Among the determined parameters are the rotational constant B 0 = 252200.8099(63) MHz and the centrifugal distortion constant D 0 = 13.2915(33) MHz, as well as two fine structure constants - the spin-rotation constant γ 0 and the spin-spin interaction constant λ 0 - together with their centrifugal distortion contributions D γ0 and D λ0 . Furthermore, each of the magnetic hyperfine parameters b F , c, and the nuclear spin-rotation constants C I were obtained for both nuclei. The accuracy of previously obtained molecular constants has been improved by up to one order of magnitude. This new set of molecular parameters allows highly reliable frequency predictions of the rotational spectrum extending into the far infrared region; such transition frequencies may be of interest for interstellar spectroscopy.

It is shown algebraically that from one set of rotational constants or moments of inertia of a complex formed by an asymmetric top molecule and a rare gas atom, eight generally different structures result which are compatible with the moments of inertia.

Experimental results are presented on the dispersion and damping of ion waves having a frequency range extending up to the ion plasma frequency. It was found that the Landau damping rate increases exponentially when the frequency of the ion wave approaches the ion plasma frequency ; while its phase velocity decreases slightly. The experimental results agree reasonably with previous theoretical predictions. The study indicates significant changes in Landau damping even with small variations in the wave velocity.

In the dynamic Lorentz-Poincare interpretation of Lorentz invariance, clocks in absolute motion through a preferred reference system (resp. aether) suffer a true contraction and clocks, as a result of this contraction, go slower by the same amount. With the one-way velocity of light unobservable, there is no way this older pre-Einstein interpretation of special relativity can be tested, except in cases involving rotational motion, where in the Lorentz-Poincare interpretation the interaction symmetry with the aether is broken. In this communication it is shown that Ehrenfest’s paradox, the Lorentz contraction of a rotating disk, has a simple resolution in the dynamic Lorentz-Poincare interpretation of Lorentz invariance and can perhaps be tested against the prediction of special relativity.

The origin of the displacement of the Fe atom in deoxymyoglobin with respect to the porphyrin plane in the high-spin state is examined by a qualitative molecular orbital (MO) analysis on the extended Hückel level. We find that attachment of a fifth ligand (imidazole in our model complex) to Fe(II)porphyrin favors the out-of-plane shift due to a strengthening of the bonding interaction between Fe and the nitrogen of the imidazole ligand. This results in a high-spin (5 = 2) ground state with Fe shifted out-of-plane for the five-coordinate complex instead of an intermediate spin ground state (5 = 1) with Fe lying in the plane for four-coordinate Fe(II)porphyrin. The relative energies of the different spin states as a function of the distance between Fe and the porphyrin plane are evaluated using an ROHF (restricted open shell Hartree-Fock) version of an INDO (intermediate neglect of differential overlap) method. We observe a level crossing between high-spin and intermediate spin states whereas the low-spin (5 = 0) state remains always higher in energy.

From an isotopic mixture of dysprosium with zero neutron scattering length and an isotopic mixture of nickel with zero neutron scattering length ribbons of the amorphous alloy Ni 56 Dy 44 were produced by melt-spinning and loaded with 59 at% deuterium. A neutron diffraction experiment yielded directly the deuterium-deuterium partial structure factor S DD and the partial pair correlation function G DD . The incorporation of the D-atoms into the amorphous matrix shows an ordering up to five coordination shells at least. The main peak of G DD is split up into a contribution at 2.36 Å with 5.4 nearest neighbours and a contribution at 2.76 Å with 4 neighbours. The D-atoms are located preferentially in Dy 4 -tetrahedra, where the occupation of two neighbouring face-sharing tetrahedra is avoided.

Magnetic susceptibility measurements and electron paramagnetic resonance spectra of samples prepared from the reactive system MnO/Li 2 CO 3 with different starting Li cationic fraction x are analyzed, taking into account the structural and compositional information provided by x-ray diffraction. Parent phases, as Mn 2 O 3 , Mn 3 O 4 and Li 2 MnO 3 , arise together with the lithium-manganese spinel as a result of Li-deficiency or Li-excess with respect to the x = 0.33 composition pertinent to the stoichiometric LiMn 2 O 4 spinel. The data show that the spinel phase can sustain a partial Li-Mn substitution in the cation sites, according to compositional models described, for x > 0.33, by Li 1+y Mn 3+ 1-3y Mn 4+ 1+2y O 4 (Li-rich spinel) and, for x< 0.33, by Li 1-|y| Mn 2+ |y| Mn 3+ 1+|y| Mn 4+ 1-|y| O 4 (Li-poor spinel). Paramagnetic resonance data of the Li-poor spinel phase are analyzed to discuss the possible oxidation state of Mn in the tetrahedral site.

The electron paramagnetic resonance spectra of Cu 2+ doped Na 2 HAsO 4 ·7H 2 O single crystals were studied at room temperature. The results indicate the substitutional entrance of Cu 2+ in two magnetically inequivalent Na + sites. Charge compensation is supposed to be fulfilled by proton vacancies. The spin Hamiltonian parameters were determined. The ground state for Cu 2+ seems to indicate the dominance of the d z² orbital and therefore a compression of the distorted octahedron along its C 4v axis.

Dielectric spectra have been measured for the title systems up to 72 GHz at 20 °C with salt concentrations ≤ 1 mol/l. The results are described by a superposition of Debye terms. Two terms are sufficient for binary water/DMSO mixtures, while two additional lower frequency ones are required when salt is added. The results for both halides differ only little. The relaxation strengths of a term ascribable to ionic complexes and a term ascribable to water/DMSO (2:1) complexes vary in opposing sense, demonstrating the competition between those complexes.

P, V m , Tdata have been measured for the smectic, nematic and isotropic phases of 4'-n-octyl-biphen-yl-4-carbonitrile (8CB) in the temperature range 300-370 K and pressures up to 300 MPa. At atmospheric pressure all phase transitions appear to be of first order due to a discontinuity in the density. The volume change at the smectic A -nematic transition is only a tenth of the volume change at the clearing temperature. At moderate pressures below 80 MPa the S A -N transition could be detected as a discontinuity in the period of oscillation in measurements with a high-pressure vibrating tube densimeter. At higher pressures the discontinuity seems to die away, possibly indicating a change from first order to second order transition. From the volume changes and the slopes of the transition lines we calculate the enthalpy changes at the phase transition. The p, V m , T data enable us to calculate the volume part of the entropy and the molecular field parameter γ=δln T NI /δln V NI .

The association-model of binary molten salt systems (M 1 ,M 2 )X 3 is critizised and the friction coefficients r 1,3 , and r 23 of the system ( 6 Li, 7 Li)Cl are calculated from ancient mobility mea-surements, showing that the coion-interactions, represented by r 12 , are about as strong as the ion-counterion-interactions, represented by r 13 and r 23.

Differential thermal analysis (DTA), differential scanning calorimetry (DSC), and the temperature dependence of the spin-lattice relaxation time (T 1 ) and the second moment (M 2 ) of 1 H and 19 F NMR were studied in (CH 3 ) 3 CNH 3 BF 4 and (CH 3 ) 3 CND 3 BF 4 . DTA and DSC revealed a solid-solid phase transition at 219 K for (CH 3 ) 3 CNH 3 BF 4 and at 221 K for (CH 3 ) 3 CND 3 BF 4 . The motions of cations and anions in the two solid phases were studied by T 1 and M 2 experiments. The motional modes of the ions and their motional parameters were determined.

The electronic structure of endohedral Sc@C 82 with a C 82 cage of C 2v symmetry has been studied by ab initio Hartree-Fock (HF) calculations. The optimized position of Sc in the configuration of minimum energy is predicted to be on the two-fold axis of the fullerene cage. In the corresponding configuration Sc is above the center of a hexagon of site symmetry C 2 . This structure of C 2v symmetry is nearly degenerate with C s and C t structures with Sc slightly displaced from the center of the coordinated hexagon. The binding energy of the endohedral complex is larger than 3.55 eV. The ab initio HF data of the C 2v topoisomer of the fullerene unit are compared with new experimental findings and HF results derived for the 3(C 2 ) topoisomer of the C 82 cage.

The shallow water wave equations (SWWEs) are of current interest in nonlinear sciences. In this paper we obtain a new family of soliton-like solutions for a (3-1)-dimensional generalized SWWE. Samples are given.

The breaking soliton equations are a class of nonlinear evolution equations of broad interest in physical and mathematical sciences. In this paper, the application of the generalized tanh method with symbolic computation leads to new exact solutions for a generalized breaking soliton equation, of which the previously-obtained solutions are the special cases.