Volume 29, Issue 5

A rarefied polyatomic gas between infinite parallel plates which is subject to a pressure gradient and to a magnetic field is considered. The tensor polarization and the Kagan polarization account for the influence of the field on the gas flow. In the slip flow regime differential equations and boundary conditions for the velocity and the tensor polarization are solved. The dependence of the solution on the mean pressure and on the magnetic field is discussed. Knudsen corrections for the Senftleben-Beenakker effect of viscosity are derived. By comparison with experimental data of Hulsman et al. a set of surface parameters is obtained. They characterize mechanical slip, thermomagnetic slip, and the influence of gas-wall collisions on the tensor polarization.

The electrical conductivity of an argon plasma in the afterglow has been measured by means of radiowave-diagnostic. The radiation of some ArI and ArII lines as well as the electron density are determined as a function of time. The relative population of the Ar lines (Boltzmann plot) are in agreement with the temperature as taken from Spitzer’s formula using the measured conductivity within errors, except at the very early afterglow. The observed intensities of the Arl lines and the measured electron density indicate that LTE exists for the excited states. However, the groundstate appears to be strongly underpopulated.

Fourier integrals are set up for the field of a point charge moving uniformly in an arbitrary direction in a uniaxial medium anisotropic in ε only. The integrals break up into several parts two of which yield the ordinary and extraordinary cones with uniform azimuthal potential distribution. The remaining integrals neither contribute to the energy radiated nor affect the size and the shape of the cones, but merely distort the field within the cones. The integrals are evaluated exactly in the non-dispersive case and closed expressions for the potential are obtained. In the dispersive case, the radiation field is determined by using the asymptotic form of the Hankel functions occurring in the integrand. The resulting expressions exhibit the high azimuthal asymmetry characteristic of anisotropic fields. From the expressions derived for a pure dielectric the potential in a doubly anisotropic medium is obtained, without a fresh calculation, by making appropriate substitutions for the coordinates of the field point and the components of the dielectric tensor.

A normal coordinate analysis of halate ions, viz. 35 ClO 3 - , 37 ClO 3 - , Br 16 O 3 - , Br 18 O 3 - and IO 3 - has been carried out using a general valence force field and Wilson’s F -G matrix approach. Mean amplitudes of vibration for bonded halogen-oxygen and non-bonded oxygen-oxygen distances have been reported using Cyvin’s method and Müller’s L-matrix formalism. Effects of isotopic substitution and isotope frequency shifts are also examined.

The rotational structures of the ν 1 bands of the deuterated monohaloacetylenes DCCF and DCCBr were investigated. The rotational constants B in the ground state and in the vibrational states involved were obtained. The centrifugal distortion constants D were calculated from the force constants and the geometrical data, too. The results D = 8.7 x 10 -8 cm -1 for DCCF and D = 1.9 x 10 -8 cm -1 for DCCBr are compatible with the experimental values (12 ± 4) x 10 -8 cm -1 and (2±2) x 10 -8 cm -1 , respectively.

The γ rays following the β-decay of 53 Fe were investigated with high resolution detectors. Two unreported weak transitions were detected at the energies 1177 ± 1 keV and 2305 ± 1 keV. Log ft values were determined and spin and parity assignments made. On the basis of the results attained, a new decay scheme was proposed. Comparison with theoretical calculations are made.

In order to determine the isotopic splittings of the vibrational frequencies of isotopieally substituted vanadium oxytrichloride and to present the correlation between VOCl 3 and VOBr 3 a set of force fields was constructed for the isotopic species of VOCl 3 , VOCl 2 Br, VOCIBr 2 , and VOBr 3 . The conventional descriptions of the fundamentals are supported by the calculated potential energy distribution in all cases. Furthermore the calculations of certain molecular constants such as the mean amplitudes, their corresponding K-values, the Coriolis coupling constants of the -type and some thermodynamic quantities have been performed.

A theory of the luminescence lifetime of a radiation-damped classical electrical point dipole near a plane interface to a medium with different optical constants is given. The influence of the interface on the lifetime of the dipole is calculated in first approximation with the methods of molecular optics. Theoretical and experimental results for a purely dielectric interface are compared.

The UV and visible absorption spectra of the ammonium salt of cupferrone and manganese, cobalt, nickel, copper and zinc divalent cupferrate complexes are investigated. The absorption bands observed are given and assigned on the basis of ligand field theory. In the UV absorption spectrum of the cupferrone metal complexes a characteristic shift in the maxima and minima appears. The effect of solvent on this shift was investigated.

The temperature dependence of electrical conductivity in amorphous selenium films is investigated. The experimental results show a polaronic conduction in the states near the Fermi level, in agreement with Mott’s model. Optical absorption measurements show the rate at which the valence band states fall off with energy into the energy gap.

3- [N- (p-Ethoxybenzilidene) -amino] -6-n-butylpyridine (ÄBBP) exhibits one nematic and two smectic mesophases. The electric conductivity of ÄBBP is studied as a function of temperature and is found to be strongly anisotropic in the smectic phases. The value parallel to the smectic layers is up to ten times higher than in the perpendicular direction. The parallel and perpendicular conductivities give different energies of activation, which is discussed on the basis of the McMillan theory.

For temperatures between 500 °C and 700 °C concentration profiles of diffusion layers have been investigated in couples containing copper and a copper-gallium-alloy with varying composition by means of quantitative electron-probe-microanalysis. From these profiles values have been derived for the growth constants k and the activation energies Q̅ controlling growth of the diffusion zone, and for diffusion coefficients D and activation energies Q of the chemical diffusion as well as for the intrinsic diffusivities D Ga and D Cu .

The photoconductivity spectrum of trigonal selenium shows a relative maximum at 0.71 μm. Measurements in the range from 0.6 μm to 0.8 μm at various quantum fluxes and modulation frequencies (4.2 - 216 Hz) indicate that two different recombination mechanisms, one at shorter and one at longer wavelengths than 0.71 μm, are operative, the former being nonlinear and the latter linear. The absorption and reflection spectra were measured too. At the wavelength of change in the recombination mechanism the depth of penetration of the radiation is about 15 μm. This depth correlates with the mean distance between the potential barriers involved in the photoactivated mobility in selenium.

Measurements of particle concentrations of Al and AlO are performed in premixed laminar H 2 /O 2 -flames with additives of organic aluminium compounds. Using the oscillator strengths in electronic-vibronic transitions of AlO published by Michels 1 , absolute number densities for different equilibria in the range 2750 - 2980 K are determined. By means of second law and third law plots a dissociation energy for AlO of 5.06 ± 0.08 eV is achieved. This value is in agreement with recent results obtained from mass spectroscopic techniques by Hildenbrand 2 .

The influence of thermodiffusion on bulb-blackening in tubular halogen incandescent lamps has been investigated experimentally for additions of methylenebromide, bromoforme or bromophosphornitrile to argon, krypton and xenon as filling gas. A strong dependence of blackening on the kind of the filling gas has been found. The influence of thermodiffusion on chemical transport may be interpreted in terms of the thermal diffusion coefficient a, which has been calculated according to Hirschfelder. Using higher concentrations of halogen, blackening of the bulb can be prevented, independent of the nature of the filling gas.

It is found on the basis of Hartree Fock calculations that the inner shell molecular orbitals of compounds that are composed of elements of the first two rows of the periodic table, are described satisfactorily by the corresponding Is atomic orbitals. Such molecular orbitals (MOs) may be substituted in a good approximation by the Is atomic orbitals (AOs). The energy of the localized MOs varies according to the type of bonding in which the atom is participating. The factors influencing the energy values may be classified in two parts; 1) the interaction with the other Is atomic orbitals and nuclii in the molecule, 2) the interaction with the valence shell electrons. Neglecting the correlation effects, both factors are considered by the calculation of the Is orbital energies. The results are compared with ab-Initio calculations done for the same molecules.

It is shown how previously reported bond energy equations (Van Hooydonk, 1973) can be regenerated starting from the assumptions (i) that the valence-orbital energy of an element in a bond can be expressed as a function of its occupancy number (Iczkowski-Margrave, 1961) and (ii) that the potential around an atom in a bond vanishes as soon as its valence orbital is doubly occupied (Ferreira, 1963). The results are consistent with an ionic approximation to chemical bonding. A comparison of the approximations involved in the present theory with those in a semi-empirical LCAO -MO method (Klopman, 1964) is advanced.

Variations of the electronic properties of nickel during the first stages of oxidation were studied by means of the soft x-ray appearance potential spectroscopy (APS). The spectra consist of a superposition of contributions from metallic nickel and from NiO and yield no evidence for a continuous change of the oxidation state of the Ni atoms. The binding energy of the 2p 3/2 -electrons in metallic nickel was found to be 851 eV and is increased in NiO by 1.4 eV. It is concluded from the shape of the APS peaks that with Ni above the Fermi level 3d- and 4s-bands are superimposed whereas with NiO these are separated in energy.

The appearance potentials (AP) of various ions, which are produced by field ionization at platinum tip emitters have been measured by a retarding potential energy analyzer coupled to the output of a single-focusing magnetic mass spectrometer. Adsorption layers of water and organic molecules on the emitter surface were found to have no significant influence on the AP measurements. The APs of the H 3 O + and (H 2 O) 2 H + ions in the water spectrum and the CH 3 OH 2 + and (CH 3 OH) 2 H + ions in the methanol spectrum suggest that the emitter surface is involved in the protonation reactions. The APs of the other ions in the water and methanol spectra have also been studied. The APs of the molecular ions of the paraffins allow conclusions to be drawn about the energy deposition function for field ionization. The fragment ions of n-heptane were found to have surprisingly low APs, up to 2.4-eV less than the molecular ion. The AP of the CH 3 + ion in the methane spectrum indicates that it arises from a surface reaction.

The transport properties of TlI and of the system AgI -TlI were investigated by measuring the electrical conductivity, σ , and the electronic and ionic transport numbers. A particularly high electronic conductivity was detected in β-TlI, while the a phase showed a predominant anionic contribution, as in TlCl and TlBr. The intermediate compounds, AgTl 2 I 3 and AgTlI 2 , are silver ion conductors, but they exhibit low σ values. A comparison with other poliiodides, with a high silver ion conductivity, is suggested on the basis of the crystal bond ionicity.

The linear and quadratic rotational Zeeman effect in orthodifluorobenzene has been observed in magnetic fields up to 25 kG. The magnetic susceptibility anisotropies are χaa- (χbb -χcc)/2 = (25.4 ± 0.8)* 10 -6 erg/(G 2 * mole) and χbb - (χcc - χaa)/2 = (29.0±0.5)* 10 -6 erg/ (G 2 * mole) ; (the c-axis is perpendicular to the molecular plane and the a-axis coincides with the twofold symmetry axis of the molecule); the molecular ^-values are gaa= -0.0412 ± 0.00'I2, gbb=0.0371± 0.0008 and gcc= +0.0163 ±0.0007. A comparison of ⊿χ = χcc- (χaa + χbb)/2 with the corresponding values of related compounds, part of which were determined by the Cotton-Mouton technique, indicates that the effect of the magnetic field on the electric polarizability of benzene - like molecules is in the order of - 1 * 10 -39 cm 3 /G 2 and should be accounted for in the evaluation of Cotton- Mouton data.

The microwave spectrum of methylthiocyanate is reinvestigated on the basis of a molecular model with five degrees of freedom, three for the overall rotation, one for the torsion and one for another vibration. It was possible to fit the splittings of all four measured states (ground state, first excited torsional and vibrational state and second excited vibrational state) with one set of parameters but it was impossible to fit the absolute line frequencies. The value for the potential parameter of the pure torsion V 3 is in good agreement with that determined on the basis of the rigid framerigid top (RF-RT) model from the ground state.

Pyrene-3-aldehyde, 3-acetylpyrene and 3-benzoylpyrene show almost no fluorescence in dilute solution in non-polar solvents. In more concentrated solutions, however, a long wave fluorescence is observed, showing the existence of weak intermolecular forces, even in the ground state. In polar solvents, pyrene-3-aldehyde and 3-acetylpyrene exhibit short wave monomer fluorescence whilst 3-benzoylpyrene does not fluoresce. The intensity for both long and short wave fluorescence is dependent upon the excitation wave length and is a maximum for excitation in the weak long wave tail of the first absorption band. Molecules are thought to have a greater absorption in this region if they interact strongly with their polar or polarizable surroundings. Due to the very short singlet lifetime of isolated monomers (τ<C10 -10 sec), such molecules have a greater probability of forming a fluorescence state than more weakly interacting ones.

The lowering of the ionization potential of singly ionized carbon has been determined from measurements of the high - pressure plasma produced by capillary - discharges in plexiglass. Line intensities of C III 2297 Å and C II 2509/2511 Å as well as the electron density from the profile of Ha were obtained side-on by the use of a rapid-scan method while the temperature of the plasma was derived from simultaneous multi-channel-measurements of the optically thick end-on radiation of the plasma column. Rather good agreement is found with the results of the theoretical approaches based on polarization-effects in plasmas.

Microwave rotational spectra of the cesium-halides have been measured in the 1 cm-wavelength region and could be extended to relatively high vibrational states. The results were combined with Gordy’s mm-mavelengths and yield the 8 Dunham energy coefficients Y 01 , Y 11 , Y 21 , Y 31 , Y 02 , Y 12 ,Y 03 and Y 04 .

Theoretical cross sections for the production of elements from 209 Bi and natural copper by high-energy proton bombardment have been calculated.

The orbital valence force field (OVFF) and the Urey- Bradley force field (UBFF) have been employed to evaluate the force constants of thio and seleno anions of VA, VB, VIB and VIIB group atoms of the periodic table. These constants were utilized to examine the relative strength of chemical bonds in isoelectronic sequences. Further, for these anions, the variation of the ratio L 12 /L 21 with the mass coupling term (T = G 12 √|G|) has been studied. This appears to be an excellent support to the extended L-matrix approximation **.

By laser excited fluorescence using extra-cavity techniques the C 2 (a 3 π u ) radical concentration in an acetylene oxygen atom flame was measured in comparison to the emission intensity from C 2 (d 3 π g ) radicals which are produced by chemiluminescent reactions.

The crystal structure of perchlorobenzocyclobutene (β-C 8 Cl 8 ) has been investigated and solved by means of the unusual Patterson projection along the axis of twinning, by which the space group had been determined. As a result of the crystal structure analysis the constitution of the molecule, derived by J. Brandmüller and E. Ziegler from spectroscopic measurements, has been found to be true.

Ab initio calculation were carried out on the singlet and triplet states of the methylnitrenium ion. The triplet state is the ground state for all values of angle at nitrogen.