Volume 30, Issue 6-7

Photoelectric atomic absorption cross sections have been calculated by means of hydrogen-like eigenfunctions for the atomic K, L, M and N sub-shells of the elements Z = 6 to 54, using revised screening constants and an extension of the theory. The absorption cross sections have been further separated into dipole and quadrupole components so that the numerical data can also be applied to the Borrmann effect.

In preceding papers it was shown that in nonlinear spinor theory cross-sections of elementary particle scattering processes can be calculated only if the state representations and their scalar products are explicitly known. To obtain these quantities, functional quantum theory of the non-linear spinor field was introduced-In this paper it is demonstrated that the introduction of functional scalar products in functional quantum theory is equivalent to impose restrictions to the spinor field operator itself concerning its groundstate behaviour. Performing this, explicit state representations of spinor field states as well as corresponding scalar products can be derived, leading thus to functional quantum theories of the spinor field in dependence on the groundstate model. It follows from these considerations that a spinor field quantum theory is in principle in-complete, as long as no additional assumptions on the groundstate are made, which cannot be derived from the general dynamics of the field.

Variational Method for Calculations of the Groundstate Energy For Hamiltonians without any symmetry properties, a variational method for the calculation of the groundstate energy is proposed. The numerical computation for the case of the few-electron-problem is based on the evaluation of functional integrals.

To treat nonequilibrium alignment phenomena in molecular liquids and in liquids crystals two points of the usual irreversible thermodynamics have to be modified. Firstly, in the specific energy a term quadratic in the alignment tensor is included. Secondly, terms up to 4th order in the alignment are taken into account in the entropy for a nonequilibrium situation. Then the entropy production is calculated. Constitutive laws are set up for the friction pressure tensor and for the tensor which characterizes the decay and the production of the alignment in the balance equation for the alignment tensor. As a first application, the nonlinear relaxation equation for the alignment is considered. For a uni-axial alignment zero and nonzero stable stationary values of the order parameter are found for temperatures above and below the temperature T K at which the transition from the isotropic to the nematic phase takes place. Small deviations from the equilibrium alignment decay exponentially. For temperatures below T K the relaxation time turns out to be anisotropic. In the appendix, the entropy associated with the alignment is calculated for a special case.

A theory is given for the spectral profile of the first hydrogen Balmer line when the radiating neutral atom is under influence of both (quasi-) static and harmonically oscillating electric fields. Profiles, measured in a turbulent heating experiment, show a series of intensity maxima on the wings of the Balmer lines. If we assume a model for the spatial distribution of turbulent wave vectors, we can derive the fieldstrength and the direction of low-frequency (ion-acoustic) oscillations and the strength and frequency of high-frequency (Langmuir) oscillations.

Potassium hydrogen sulphate single crystal has been γ-irradiated at room temperature and its electron spin resonance spectrum recorded by changing the H 0 static magnetic field, around an orthogonal axes system. The electron spin resonance spectrum is a single line with a slightly anisotropic g factor. The paramagnetic species has been identified as SO 3 - and the principal values of the g tensor has been determined as g 1 =g 2 =2.0060, g 3 = 2.0045. Direction cosines of the principal values of the g tensor with respect to the chosen axes have been determined. The spin-orbit contribution to the g-factor has been explained.

Spin Lattice Relaxation in the Triplet State of Qainoxaline in Perdeuteronaphthalene and of two Similar Mixed Crystals The spin lattice relaxation in the excited triplet state of three mixed crystals was investigated: Quinoxaline in perdeutero-naphthalene, quinoxaline in naphthalene (X-traps) and quinoxaline in durene. They differ by the depth of their traps, which are shallow (90 cm -1 ), very shallow (60 cm -1 ) and deep (6600 cm -1 ), respectively. In order to identify the relaxation processes and the relaxation mechanism, the experiments were performed in the large magnetic field range be-tween 0.2 T and 5.4 T. By use of a non-resonant optical method and by ESR and ODMR it could be shown that at high fields the direct process (emission of resonant phonons) is the only efficient process up to 4.2 K. At low fields Raman-processes are dominant. Thereby the spin lattice relaxation probability per unit time, w, increases with the ninth power of the temperature in the shallow trap systems and with the fifth power in the deep trap system. By the analysis of the very strong anisotropy of w it could be shown that the efficient relaxation mechanism in the shallow trap systems is a guest-host-interaction modulated by phonons.

Structure By transmission of Mo-Kα-radiation, intensity curves were obtained from molten Al and molten In as well as from Al-In alloys containing 10, 20, 30, 40, 70, 80, 90, and 95.3 a/o Al. Radial distribution functions were calculated from these experimental curves. From the RDF's the con-centration dependency of the number N I and the distance r I of nearest neighbours was obtained. The concentration dependency of nearest neighbours reveals the segregation tendency of molten Al-In alloys. The small angle scattering observed in the intensity curves is in agreement with this result and will be treated in a subsequent paper.

By means of small angle X-ray diffraction work it was revealed that ball-shaped segregated regions with diameters of 8 up to 10 Å exist in molten Al-In alloys. Interpretation of segregated regions as originated by concentration fluctuations shows, according to the method of Ornstein-Zernike, that the correlation length is approximately 3 Å. According to the method of modulation of monotonic Laue scattering, positive values between 0.04 and 0.2 for the coefficient of short range order were obtained. Apparently the melts consist of a matrix with statistical distribution of the atoms of both kinds together with two kinds of ball-shaped segregated regions, one kind containing only Aluminium-, the other only Indium-atoms. A plot showing the variation of volume concentration w AIT of Aluminium regions versus total concentration w T of regions of any kind is given: w T may reach from 0.2 up to 30 vol.-%.

The adiabatic velocity of ultrasound u in molten AI, In, and Al-In alloys was measured at various concentrations and temperatures. For the alloys the u(T) curves consist of two linear regions with a transition region. The function ⊿u/⊿T and the compressibility versus concentration show positive deviation from linearity. In the latter case the deviation at 1000 °C is smaller than that at 880 °C. The partial structure factors a ij (O) were obtained, a Al,Al (0) and a In,In (0) showing rather high positive, and a Al,In (0) rather high negative values. Thus the segregation tendency becomes obvious. This also can be deduced from the plot of Nń [which is a linear combination of the a ij (0) ] versus concentration.

Results of a molecular dynamics study of an aqueous CsCl solution are reported. The system consisted of 216 particles, 200 water molecules, 8 cesium ions and 8 chloride ions and was run over 8000 time steps equivalent of 9 · 10 -13 sec. On the basis of radial pair correlation functions, average potential energy of the water molecules and pair interaction energy distribution the static properties of the first hydration shells of the ions are discussed in detail. The self diffusion coefficient for the water molecules is calculated and compared with NMR measurement as well as with molecular dynamics calculations for pure water at elevated temperatures and pressures.

The specific electric conductivities and densities of molten ZnCl 2 -SnCl 2 binary mixtures were measured as a function of composition in the temperature range 260 -530 °C. The electric con-ductivities show small, mainly negative, deviations from additivity. The densities show positive deviations from additivity, especially in the SnCl 2 -rich composition range. The structural properties of the melts causing such a behaviour are discussed.

X-ray diffraction patterns have been measured on molten alkaline earth metals (Mg, Ca, Sr, and Ba) in the temperature range from the melting points to 880 °C. In all cases the structure factors obtained were temperature insensitive. By the usual Fourier transformation of the structure factors, the atomic radial distribution functions were evaluated. From these the interatomic distances and coordination numbers were estimated. The structural information was applied to a discussion of the electron-transport properties using the Ziman theory.

Short-range interactions of Electrolyte Solutions Short range interaction potentials between ions are approximated by a step function with a hard core. Then from general statistical-mechanical formulas the first correction to the limiting law of the free excess energy F* (S (2) -term of the cluster theory) is computed for low concentrations, i.e. small plasm parameter μ=e 2 x/D 0 kT ⪡ -. Fitting to a Lennard-Jones potential for symmetrical electrolytes results in values for F*, the osmotic pressure and the osmotic coefficient. Numerical fitting to experimental results of Lange for the osmotic coefficient gives information concerning the contact distance a and attraction parameter E for some water-tetraalkylhalogenide-systems.

The capture of thermal electrons by the molecules CH 2 Cl 2 and CHCl 3 is reinvestigated and discussed. An attempt is presented to describe the reaction path in terms of potential energy diagrams.

The ESCA spectra of several substituted benzenes and heterocyclic compounds were obtained. Multi peak structures are observed in the various energy regions. The effects are generally interpreted as due to shake up phenomena involving intramolecular charge-transfer transitions between a "donor" and an "acceptor" group in the molecule. A quantitative model for such kind of phenomena is given. It rationalizes the fact that: 1) These shake up processes are, to a large extent, specific to the atoms of the acceptor groups; 2) the shake up energies found for the atoms of the donor part of the molecule (E D ) are generally higher than that (E A ) observed for the atoms pertaining to the acceptor group; when it is possible to correlate the shake up transitions to an U.V. one, the energy of the ultraviolet absorption transition seems generally intermediate between E D and Ex. The analytical, spectroscopic and chemical importance of multi peak structures of ESCA bands is emphasized. In particular, the fact that it is not generally recognized that the shake up phenomena may cause strong broadening of the bands is criticized in connection with both the evaluation of ionization energies and the deconvolution procedures.

Demixing phenomena were studied in 12 mixtures type LiF + (Me I , Me II )Br, Me I and Me II being alkali metals. Previous measurements of the LL equilibria in the system LiF + CsBr were extended to the high temperature field to evaluate the position of the point of maximum. Moreover, the data obtained on the system LiF + NaBr were analyzed in order to calculate the critical temperature of the "submerged" gap. The results allowed to test the thermodynamic theories concerning the reciprocal ternary systems in the case of large deviations from ideality.

Microstructures of polycrystalline hexagonal close packed (hep) Zn and Mg have been studied by x-ray diffraction line broadening analysis using the integral breadth method, and the Fourier coefficient method. For these two methods, several diffraction peaks were considered to obtain two suitable peak combinations. For the room temperature powder samples, the root mean square (rms) strain was observed to be extremely small. The particle size was anisotropic in both samples with the Zn powder showing more particle size variation than Mg. The average particle size for Zn was about 750 Å, which was over twice the average particle size of 295 Å observed in Mg. The two fault probabilities for Zn turned out to be negligible or zero. Mg, on the other hand, was found to have small, but definite fault probabilities. The deformation fault probability a was 4.5X10 -4 and the growth fault prob-ability β was 6.5X10 -4 . These results can be compared with the previous work of hep Cd at room temperature, which was found to have no growth fault probability β and a deformation fault prob-ability a amounting to 3X10 -3 . This value is higher than that observed in Mg, because for Cd the two fault probabilities were obtained by neglecting the particle size of about 650 Å which actually did exist in the sample.

Using a simple home built apparatus, the surface contamination of various samples maintained at high vacuum conditions is investigated by means of SIMS technique. On a polycrystalline copper surface, at a sample temperature of about 140 K, residual water vapour condensation occurs and ions H + (H 2 O)n with 1≦n≦11 appear in the positive ion spectrum. On the contrary, on a LiF crystal no water contamination is observed down to 120 K; moreover, on a KI sample, one of the most hygroscopic salts among the alkali halides, only at 130 K an appreciable H 2 O contamination is detected.

Mixtures of O 3 with excess N 2 O were photolysed in the wavelength region 290 - 335 nm using monochromatic light with a band width of 4 nm. The resulting primary product atomic singlet oxygen, O( 1 D), in reacting with N 2 O produces in part NO which subsequently reacts with O 3 giving rise to a weak infrared chemiluminescence. The emission was monitored with a cooled photomultiplier. The emission intensity is directly proportional to the rate of O( 1 D) production and it has been utilised to derive the relative O( 1 D) quantum yield as a function of wavelength between 295 and 320 nm. The data were normalised to a quantum yield of unity of 300 nm and corrections were applied to reduce the error resulting from the spectral band width of photolysing radiation. The O( 1 D) quantum yields show a temperature dependence. At 298 K the quantum yield is unity up to 305 nm, then declines to zero at 319 nm. At the dissociation limit, taken to occur at γ = 310.3 nm, the quantum yields is 0.57, i. e. considerably below unity. The implications of this result as well as the tail toward longer wavelengths and the temperature dependence are discussed. Ozone absorption cross sections are also reported.

An ionic, i. e. essentially electrostatic, approximation to donor-acceptor bonding between neutral species, ion-molecule interactions and corresponding solvation effects is forwarded. Drago's E-C equation for donor-acceptor reactions and the elimination of solvation procedure (ESP), presented by Drago et al., can consistently by incorporated in the general scheme. The theory yields further correct values for bulk ion-solvation enthalpies of cations H + ,Li + ,Na + ,K + ,Rb + in water with the aid of ionization energies and electron affinities only. The formulae deduced for these types of chemical bonding represent the equivalent of the electronegativity-based theory for the description of ordinary chemical bonding between atoms, introduced earlier.

Macroscopic slip velocity, macroscopic temperature jump, thermal creep velocity and diffusion slip velocity for a mixture of monatomic gases are calculated by using a method developed recently (modified Maxwell-method) for a general gas-gas and gas-surface interaction law, and for a possibly anisotropic surface. The results are expressed in terms of accommodation coefficients of first and second order. Specialization is made for a binary gas mixture. For a comparison the results obtained by Maxwell's original method and general surface accommodation are given. In the case of surface-anisotropy several new slip effects occur.

A time-of-flight technique is used for the measurement of positive ions mobilities in helium, neon and argon in the 1 - 25 atm pressure range at 25 °C. The reduced mobilities b 0 vary with the reduced electric field E/p 0 and exhibit different saturation values, which are interpreted in terms of the Langevin theory and connected with the formation of cluster ions: He + 33 (b 0 = 7.4 cm 2 /Vs), Ne + 13 (3.1), Ne +33 (2.25), Ar + 13 (1.23) and Ar + 33 (0.82). In Argon also the reduced mobility of Ar + and Ar + 2 were measured: b 0 = 1.56 and 1.84cm 2 /Vs.

In water-ethanol mixtures hypersound velocities and hypersound damping were measured at 10°, 20°, and 25 °C by Brillouin scattering. From the experimental data the relaxation frequency and the noerelaxing fraction of the bulk viscosity were calculated.

A statistical variation-perturbation method is used in the derivation of multipole polarizabilities from Hartree-Fock electron densities. A quantum correction of the kinetic energy expressions takes into account the exponential decrease of the electron density in the outer part of the atom. The method is called semiempirical because of the still unsolved problem of the kinetic energy in the statistical theory of the atom. The results are compared to the best available experimental and theoretical values of dipole-and quadrupole-polarizabilities and show agreement within approxi-mately 10 - 15 percent. They are lower than Hartree-Fock perturbation results. As the numerical calculations are reduced to single integrations, the mathematical labor is considerably reduced. In an appendix dipole polarizabilities are calculated in the framework of the Gombas model including exchange and correlation for ionization degrees from zero to six.

The electron relaxation times T 1 and T 2 have been measured by ESR pulse techniques in solutions of normal and perdeuterated (diphenyl) - in dimethoxyethane at various radical concentrations and temperatures. The results are discussed in terms of different relaxation mechanisms. The most important contribution to spin-lattice relaxation at high concentration is dipolar interaction with other radical electrons modulated by translational diffusion. Spin-spin relaxation has in addition contributions from electron exchange and ion pairing.

The basic idea of this article is that in a bilocal field theory the Lorentz group can be replaced by the larger group SO (4;4) which contains SO (3;1) as a subgroup. On this basis a system of 24 coupled differential equations is introduced. In the special case of the pion the connection with the local field theory is discussed. It turns out that the application of the local field theory is limited by the reduced Compton wave length λ/2 π of the pion.

An analysis was made of the demixing phenomena in the reciprocal ternaries Li, Me/Br, F (Me = Zn, Pb, Cd). It was found that the system Li, Zn/Br, F shows only a "tendency" to demix; the system Li, Pb/Br, F exhibits a miscibility gap (MG) which could be completely detected in the whole composition square; finally the system Cd, Li/Br, F shows a MG which was only partially measured along the stable diagonal. The trend in demixing of these systems agrees with the values of the standard enthalpy variations of the metathetical reactions.

The profiles of the HeI line λ=4471.5 Å (4 3 D-2 3 P) and its forbidden component λ=4470 Å (4 3 F - 2 3 P) have been measured for electron densities Ne ranging from 7 · 10 14 cm -3 to 3 · 1O 16 cm -3 . The line was emitted from a continuous afterglow plasma emerging from a plasmatron device. The working pressure ranged from 100 Torr to 2 atmospheres. Our measurements agree with those of Bekefi et al. (1971), Bretagne et al. (1971/1973) and Drawin and Ramette (1974). Relatively by large discrepancies are found with some theoretical calculations. Our measurements include the very interesting density region from N e =2 · 10 15 cm -3 to Ne = 1 · 10 16 cm -3 for which only a very few experimental data are available.

The microwave spectra of (CH 3 ) 2 15 NNO, (CH 3 ) 2 N 15 NO, syn- 13 CH 3 12 CH 3 NNO and anti- 13 CH 3 12 CH 3 NNO have been studied and the rotational constants evaluated. With these data and former results 1 the r s -structure of the carbon-nitrogen frame has been found to be planar. An r 0 -structure has also been calculated. From the hyperfine structure of the spectra the nuclear quadrupole coupling constants of the nitrogen nuclei have been determined. Further studies to complete the r s -structure are in progress.

The kinetics of M A g 4 I 5 (M=K, Rb, NH 4 ) formation from β-AgI and MI are investigated on pellets by the contact method. For all the three reactions involved, the governing mechanism is found to be the cation counter-diffusion while the rate-determining step is the diffusion of M + . On the basis of Wagner's theory the self-diffusion coefficients of K + , Rb + and NH 4 + are evaluated in the three compounds.

The temporal growth rates are calculated for side-scat-tering of light by modes near the upper and lower hybrid frequencies in a turbulent, inhomogeneous plasma.

The influence on spectral line profiles of a possible coupling between the low and high frequency parts of the plasma microfield, and of ternary plasma correlations is investigated. Both effects may have some importance in high density plasmas (e. g. arc experiments), but the first of them is shown to be generally predominant.

Results of measurements of the viscosity and of the molar volume for the ideal liquid system chlorobenzene + bromo-benzene are presented. They cover the whole composition range between 0 °C and 80 °C. Both the composition and the temperature dependence of the viscosity are discussed.

Using a retarding potential energy analyzer the appearance potential of doubly charged benzene ions formed by field ionization was found to be 14.0 ± 0.3 eV. This appearance potential supplies evidence for the desorption of C 6 H 6 ++ ions in a chainlike structure from the surface of the field anode.

A novel interferometric mode selector allows easy alignment and stable operation of a cw dye ring laser. Details of its function in multimode and single mode operation are described.