Band 47, Heft 3

A numerical study of the flow after impulsive load of a plane material surface is carried out. It is shown that the flow is asymptotically self-similar provided one can neglect the cold components in the equation of state. In this case the effective exponent s(t) = d l n (X s ) / d ln(t), derived from the shock trajectory X s (t) does not depend on the initial pressure pulse and approaches the exponent α of the self-similar problem for time t →∞. For equations of state containing a cold pressure term, s (t) is larger than α and changes non-monotonically with time. Some features of the flow related to the presence of cold components in pressure and internal energy are discussed.

The wavelengths of the L series of argon, krypton and xenon, the K series of argon, and the M series of curium were measured by means of wavelength dispersive X-ray microanalysis. The specimens for the investigations were TiC layers which had been HF sputtered under reduced argon pressure by the PVD method, krypton and xenon implanted zeolites, and a curium doped borosilicate glass. The obtained relative intensities of the X-ray emission lines were normalized to the maximum intensity of the line of the respective series

Lyoluminescence, the radiation induced light emission during the dissolution of irradiated solid substances like alkali halides, saccharides, amino acids etc. was proposed as a method of dosimetry. It is established that lyoluminescence is a consequence of a reaction of radicals from radiolysis with oxygen dissolved in the solvent. The role of oxygen in the lyoluminescence of saccharides has been investigated. It has been proved that oxygen is not only necessary for the chemical reaction preceeding the lyoluminescence process, but that it is also the emission centre itself. Singlet oxygen is released from the disproportionation of peroxyl radicals produced during solution. The lyoluminescence emission peaks may be attributed to the simultaneous transitions [ 1 Σ g + ] [ 1 Σ g + ] , [ 1 Δ g ] [ 1 Δ g ] and [ 1 Σ g + ] [ 1 Δ g ] to [ 3 Σ g + ] [ 3 Σ g - ] of collisional pairs of singlet oxygen molecules

Two lower bounds for the free energy of the Hubbard model are compared

Absorption transition moment directions of the diphenylphosphinyl (2 a) and methylsulphonyl (3 a) ω-substtuted in 4-dimethylamino-trans-styrenes were determined in stretched poylvinyl alcohol (PVA) films based on measurements of the absorption anisotropics. It has been found that the long-wave absorption spectrum consists of two bands corresponding to differently directed transition moments. The transition moment of the intensive long-wave 1 L a band is lies along the long axis of these molecules whereas that of the short-wave 1 L b band is oriented at φ= 38° for 2 a and φ= 35° for 3 a relative to the transition moment direction of the 1 L a band

The ν 8 band of CF 2 NH near 830 cm -1 has been measured with a resolution of 0.003 cm -1 and rotationally analyzed. The band is unperturbed, and its rovibrational parameters are given up to fourth order. Theoretical harmonic and anharmonic force constants have been calculated at the 6-31 G ** SCF level, and all vibration-rotation interaction constants α i and anharmonicity constants x ij are predicted. The theoretical results are compared with the available experimental data

The electric dipole, quadrupole, octopole and hexadecapole moment of carbon monoxide has been obtained from finite-field SCF and Moeller-Plesset perturbation theory calculations. The resulting values for the octopole and hexadecapole moments of CO(X 1 Σ + ) are 3.59 ea o 3 and - 9.01 ea o 4 respectively

Raman and X-ray scattering experiments have been performed on an aqueous zinc (II) bromide solution with molar ratio [ H 2 0] / [ ZnBr 2 ] =10 at 25 to 140 °C. The intensity of the totally symmetric Zn - Br stretching vibration (ν 1 ) for the dibromozinc(II) complex increased with increasing temperature while that for the tetrabromo complex decreased. A broad band assigned to the symmetric Zn - O stretching vibration ( ν 1 ) for the aqua zinc (II) ion decreased in intensity with increasing temperature. The X-ray diffraction data revealed that the average number of the Zn - Br interactions within the zinc (II) bromo complexes does not change with temperature, whereas the number of Br ··· Br nonbonding interactions within the complexes decreases from 1.8 at 25 °C to 1.5 at 100 °C. From both Raman and X-ray data it is concluded that with increasing temperature the dibromo species is favored, whereas the tetrabromo and aqua zinc(II) species are unstable in the solution. The analysis of the X-ray diffraction data has shown that the mean Zn - Br bond length within the zinc (II) bromo complexes shortens gradually with increasing temperature, accompanied with an increase in the interligand Br ···Br distance. This finding suggests that the Br - Zn - Br bond angle increases with decreasing Zn - Br distance for the lower zinc(II) bromo complexes. The equilibrium shift of the zinc (II) bromo complexes with temperature is discussed on the basis of ion-ion, ion-water, and water-water interactions

Conductance measurements of aqueous solutions of succinic acid and of di-sodium succinate were performed from 278.15 to 308.15 K and the limiting conductances λ 0 (1/2 Succ 2- ) are reported. The Waiden product is independent of temperature: λ 0 (1/2 Succ 2- )*η(T) = 0.503 ± 0.001. The salt conductances closely obey the Onsager limiting law. The evaluation of the equilibrium constants for the primary and secondary steps of dissociation, K 1 and K 2 , and the limiting conductances of the hydrosuccinate ion, λ 0 (HSucc - ), are discussed using the Quint and Viallard conductance equation

The high-resolution FT-IR spectrum of the A-type fundamental ν 11 of furazan ( C 2 H 2 N 2 0) has been recorded and analysed against the background of rotational information from DRM microwave spectroscopy to yield the band origin as ν 11 0 = 1175.3377 + 0.0001 cm - 1 . The combined use of microwave (MW) and FT-IR data gives this band origin with a statistical uncertainty of σ= 10 -6 cm -1 and leads to a refinement of the rotational constants of the state ν 11 = 1 over those derivable from either MW or FT-IR data alone

We reinvestigated the microwave spectrum of cyclopropylbromide with the increased resolution of pulsed microwave Fourier transform spectroscopy. Because of the higher frequency precision, it was possible to determine the spin-rotation coupling constants of bromine. Global fits of rotational constants, quartic centrifugal distortion constants, quadrupole coupling constants including the off-diagonal component χ ac , and spin-rotation coupling constants simultaneously to almost one hundred hyperfine components for each of the two bromine isotopomers resulted in overall standard deviations of well below 5 kHz

The two-nuclei quadrupole hyperfine structure of four 2 Q 1 -subbranch transitions of deuteroisothiocyanic acid, DNCS, has been resolved and analyzed by use of a waveguide microwave Fourier transform spectrometer. The analysis yielded one previously unknown quadrupole coupling constant ( χ - ≡ χ bb -χ cc ) for both nitrogen ( χ - N = +27.6(11) kHz) and deuterium X - D = +175.8(11) kHz). Taking into account the results from earlier work on HNCS, DNCS, HNCO, and DNCO, the orientations of the principal axis systems of the two quadrupole coupling tensors could be calculated. It appears that while the deuterium tensor is aligned to the D-N internuclear axis as expected, the nitrogen tensor is tilted away from the bisector of the DNC angle by 13° towards the NCS chain

Liquid Crystalline Aromatic Cholesterol Derivates A series of aromatic cholesteryl ethers, esters, phenylcarbonates and benzylcarbonates were prepared and their liquid crystalline properties studied. The occurence of ferroelectric phases as well as properties of cholesteric and blue phases alternate with the number of linking atomes between steroid and atomatic system

The absorption and luminescence static and dynamic properties of a group of quinolizinone and indolizinone derivatives in solvents of different polarity at 297 K and 77 K are studied. On the basis of the spectral data and the PPP quantum-chemical results the problem of the main chromophore in these structures is discussed

Acetone is a molecule with an intermediate barrier for methyl- top internal rotation, and only molecules in the A 1 A 1 - state of the tunneling motion exhibit a rigid rotor spectrum. For this state we report the results of a rotational Zeeman effect study of acetone in exterior fields up to 20 kGauss (2 Tesla). From an analysis of the observed Zeeman splittings within the asymmetric top approximation the nonzero elements of the g-tensor and the magnetic susceptibility anisotropies were obtained as follows: g aa = -0.04379 (8), g bb = - 0.06611 (5), g cc =-O.O1481 (7), 2ξaa -ξbb - ξcc = - 9.53 (21) 10 -6 erg G -2 mole -1 and 2 ξ bb - ξ cc - ξ aa = 25.57 (18) 10 -6 erg G -2 mole -1 . The nonzero elements of the molecular electric quadrupole moment tensor were derived as Q aa - 2-77 (13) DÅ, Q bb = -4.59 (10) DÅ and Q cc = 1.82 (15) DÅ. Zeeman spectra were also recorded for seveal low-J transitions of molecules in the EE-state of methyl top tunneling (one top tunneling), and so far the same splittings have been found as for the A 1 A 1 -species

The effect of temperature on the fluorescence quenching of perylene has been studied in a variety of two-component mixtures of CCl 4 with cyclohexane and benzene. Results of these studies are explained in terms of specific interactions between the components of the mixtures

A unified theoretical description of static and dynamic properties of ferroelectric liquid crystals in terms of a Landau free energy is presented. The shear deformation tensor is used as principal order parameter. Results for the stationary case for tilt angle variation and dielectric properties are compared with experiments on a compound with a pronounced first-order SmA-SmC* phase transition for various strengths of the applied electric field

The stability of the liquid state of aqueous lithium salt solutions was studied with a modified DTA technique. Aqueous solutions of LiCl and LiSCN in the concentration range 8-14 mol kg -1 , LiBr in the range 8 - 10 mol kg -1 maintain their liquid state for at least 50 hours at temperatures slightly above their glass transition points