Band 31, Heft 9

The coefficient matrices in the transport-relaxation-equations (moment equations of generalized thermo-hydrodynamics) depend on the polynomials used in the expansion of the underlying kinetic equation. The known behaviour under time reversal of these polynomials, Eq. (7), entails symmetries of the fore-mentioned coefficient matrices, Eqs. (12) and (16). From these symmetries a reciprocity theorem for two stationary solutions of the transport-relaxation-equations is derived, Eqs. (21 a und b) : the divergence of a certain vector field, bilinear in the two solutions, vanishes. The relaxation matrix does not appear in this form. The theorem is useful for investigating the proliferation of the Onsager symmetries from the basic differential equations into the linear algebraic relations between the few global quantities governing “discontinuous systems”. A simple example in heat conduction is worked out. A more complicated case and the role of a magnetic field are briefly considered. Equivalent with (21 a) is the kinetic reciprocity theorem (40).

A nonlinear inhomogeneous relaxation equation for the alignment tensor is derived from a Fokker-Planck-equation for the orientational distribution function where torques exerted by a molecular field and by the gradient of the flow velocity are taken into account. Phenomenological coefficients characterizing the flow alignment in the isotropic and in the nematic phases are related to molecular parameters.

A kinetic model for a weakly-ionized plasma interacting with radiation is proposed based on the energy-momentum method, in which both energy and momentum of the system are conserved. The radiation-initiated ionization is obtained in a non-inertial coordinate system, and the proposed model satisfies the H-theorem.

To evaluate the thermal conductivity of a hydrogen plasma at atmospheric pressure, previously reported results of experimental end-on spectroscopic temperature measurements are corrected for the influence of the schlieren effect. New thermal conductivity data for hydrogen are given.

Fourier transform NMR studies of 17 O, 35 Cl, 51 V, 53 Cr, 55 Mn and 95 Mo are reported for aqueous solutions of the oxyanions ClO 4 - , VO 4 3- , CrO 4 2- , MnO 4 - , and MoO 4 2- , partly enriched in 17 O. The indirect spin-spin coupling constant between 17 O and the quadrupolar central nucleus is determined: A linear dependence of the reduced coupling constants on the atomic number of the central nucleus in the isoelectronic series VO 4 3- , CrO 4 2- and MnO 4 - was found.

The He (I) photoelectron (PE) spectra of indene, indole, benzofuran, benzothiophene, 1-, 2-, 3-, 4-and 6-methylindole and 4,5,6,7-tetrafluoroindole were measured and analysed. A close correlation between the π-ionisation energies of these compounds and the eigenvalues of the corresponding HMO-orbitals is found. A qualitative scheme for the assignment of the π-electron ionisations by orbital interaction of the constituents of the indene analogs i. e. of styrene and the p-orbital of the corresponding heteroatom, indicates that the energy levels in all the compounds investigated can be described by the same type of interaction and yields a value for the inductive effect of the hetero group (-CH 3 and >CH 2 : 0.3 eV, >NH: 0.4, >S: 0.1, >O : negligible).

The absorption behaviour of Mn 2+ -ions in CeO 2 has been investigated and interpreted for the first time. Beside the hyperfine-multiplett with selection rules ΔM =1 and Δm = 0 we observed forbidden transitions with ΔM = 1 and Δm=± 1 At T = 29Q K the line width is rather small and amounts to 2.5 G. The entire spectrum can be described by an isotropic spin-Hamilton operator with g=1.9989 and A = 86.36·10 -4 cm -1 . It is shown for Mn 2+ in the crystal-field of oxygen-ions that there is a linear relationship between the hyperfine coupling constant A and the coordination number.

It is shown that local modes due to C 13 -and N 15 -Isotopes in their natural abundances of 1.12% and 0.36% in K 3 Cu(CN) 4 can be observed by the frustrated total reflection technique (FTR) in spite of almost vanishing mode strengths. The observation is made possible by the dispersion of the polariton brandies which reduces the reflectivity in the resonance region.

A novel method is described for compensation of size variations in the input pattern of an optical correlator for pattern recognition by appropriate adjustment of the reconstruction wavelength. Simple ring-shaped patterns of variable diameter have been optically cross-correlated. Using a tunable dye laser of narrow bandwidth, the correlator output was analyzed for various combinations of size and wavelength to show the performance of the method.

Precise molecular dynamics calculations on molten potassium chloride have been performed using Born-Mayer-Huggins pair potentials and periodic boxes containing 216 ions. It is found that the function (2 E k - ψ)/3V, E k being the kinetic energy, the instantaneous virial and V the volume, respectively, which on averaging yields the pressure, fluctuates by ± 2000 bar due to the fluctuations of the exponential term ψ ex of ψ .To base the calculated pressure and velocity auto-correlation functions on good statistics, it seems necessary to reduce these fluctuations by increasing the periodic boxes.

The angular distributions of the water dipoles have been calculated from molecular dynamics runs for the first hydration shells of various ions in 2.2 molal LiJ, LiCl, NaCl, CsCl and CsF solutions and in a 0.55 molal NaCl solution. It is shown how the distributions depend on the size of the shell taken around each ion. The results give no indication for the existence of desoriented water molecules in the immediate neighbourhood of the ions.

Determinations of the initial thermoelectric power were carried out at 1000 K in the whole composition range of the molten systems AgI-Ag 2 XO 4 (X = Mo, W). For the composition X AgI = 0.8 the investigation was extended to the variation of the thermal emf at the “melting point” of the electrochemically noteworthy glass-like phases, obtained through rapid quenching of the melt. The hypothesis that these glass-like materials could keep the melt configuration at room temperature is contradicted by the results on the molten systems; more complex interpretations, based on the behaviour of the thermal emf at the “m.p.” are proposed.

By means of an “ab initio” all electron treatment of the I - /H 2 O complex in various geometrical arrangements, it has been attempted to derive some arguments for the general discussion about the phenomenon of negative solvation, based on the background of quantum chemistry. The most stable conformation of the complex is indicated to have C 2 v symmetry. Rotating of this conformation by 180° leads to an arrangement whose destabilization energy has about the same value as the complex formation energy, which, on the other hand, is only slightly higher than the hydrogen bond energy between two water molecules. These results contradict the formation of an almost rigid first hydration sphere and allow, further, the interpretation of the negative solvation by means of a “cooperative effect” between ion-solvent complex and other solvent molecules, in full agreement with the work of Engel and Hertz.

The dielectric properties of Cu(gly) 2 and Cu(glygly) in diluted aqueous solution were examined in the MHz range at 273 to 313 K. The complexes exhibit dielectric absorption in the ranges 5.09X10 7 to 9.34X10 7 Hz and 4.63X10 7 to 8.01X10 7 Hz, respectively, depending on concentration and temperature. This absorption was attributed to rotational relaxation of the unhydrated and monohydrated complexes. The following data for the two complexes in solution at 293 K have been obtained, respectively: dipole moment 19.3 D and 34.0 D, charge separation 2.01 A and 3.54 Å, relaxation time 2.3X10 -9 sec and 2.6X10 -9 sec, molecular radius 6.36 Å and 6.47 Å, activation energy for the relaxation process 5.6 kcal mole -1 for both complexes.

The characteristic ferroelectric dispersion of the complex dielectric constant of AgNa(NO 2 ) 2 is measured in a wide temperature range enclosing the transition point. It can be well described by a Debye monodispersive process except for a small temperature intervall around T c . The relaxation strength obeys a Curie-Weiss law in the paraelectric phase, whereas in the ferroelectric phase there are deviations from this behaviour. A first order phase transition is observed which is close to a second order one. The maximum value of the dielectric constant at T c is 10 4 .

The theory of dispersion energy has been shown to directly give an explicit expression for the solvent shifts in the spectra of non-polar solute molecules.

Stationary and modulated IR-ATR spectra of Schiff's base nematic liquid crystals are reported. The mean order parameter of both, the aromatic core and the hydrocarbon chains is determined by analysis of the infrared dichroism of characteristic absorption bands. Hydrocarbon chain ordering was found to be considerably lower than predicted by Marčelja's statistical theory.

The subject of the present paper is computer simulation of a-solid and liquid nitrogen, using a Lennard-Jones atom-atom potential and the isothermal-isobaric Monte-Carlo method. Two sets of calculations were performed, both at the same pressure (1 atm) and temperatures (a-solid at 25 and 35.6 K, liquid at 63.15 and 77.35 K). In the first set the molecules are assumed to be rigid, whereas in the second they are allowed to vibrate; the molecular vibration is treated classically and as-sumed to be harmonic. Comparison are mode between the two models and with experiment.

The rotational spectrum of the planar cis rotamer of formic acid, cis-HCOOH, has been detected for the first time. Twenty transitions belonging to the q R K, q Q 1 , q Q 2 , r P 0 , r P 1, r P 2 branches of the parent isotopic species in its ground state have been assigned and measured. The rotational constants and quartic centrifugal distortion constants have been determined using Watson's reduced Hamiltonian. Stark effect measurements have yielded the molecular electric dipole moment: μ a = 2.65(1) D, μ b = 2.71(1) D and , μ= 3.79(1) D. The energy difference between the ground vibrational states of cis-and trans-HCOOH has been determined by microwave relative intensity measurements. The cis rotamer is found to lie at higher energy than the trans rotamer by 1365 ± 30 cm -1 . A one dimensional potential energy curve has been calculated for the OH torsional vibration of formic acid.

The pressure dependence of the lower hybrid resonance is investigated in a hydrogen plasma generated by a high frequency discharge. Appreciable shifts of the absorption peak with the neutral gas pressure are observed only in a mirror like magnetic field configuration. The measurements show that this shift cannot be explained by a change of the ion composition of the plasma, but must be attributed to two other mechanisms: The composition of the spectrum of the kn-components is influenced by the axial electron density profile so that at low pressure the higher modes of the spectrum are dominant.With higher pressure the formation of radial modes is favoured which leads to an additional apparent shift of the resonance.

The spectral radiance of a deuterium lamp has been calibrated by the radiation of an electron synchrotron and by the continuum radiation of a high temperature hydrogen arc. The two measurements allow an indirect comparison of the two radiometric standards in the spectral range from 175 to 340 nm. They agree with each other within less than ± 5%.