New interferometric method for determining the refractive index of thin dielectric film,its thickness,the phase shift,and the order of interference

A new interferometric method is proposed, using white light fringes of equal chromatic order to determine simultaneously the following paramcters:

1. The refractive index of a thin dielectric film, and hence its dispersion.
2. The film thickness.
3. The correct value of the order of interference.
4. The phase shift occuring due to reflection at the dielectric/metal interface. In the present work, doubly silvered zinc sulphide (ZnS) thin dielectric film was used as an example in applying the proposed method.

     

Bestimmung der wahren Halbwertsbreite derMζ-Linien der Elemente 38 Sr bis 47 Ag

1. The intensity distribution of theMζ-lines (40<λ<110Å) was measured using a 2m concave grating spectrometer.
2. The instrumental profile of the spectrometer could be determined by solving a modified folding equation by the method of successive approximations. For the spectrometer used we found that the instrumental response was a Gaußian, and that its width is independant of wavelength.
3. A graphical method is applied by which the natural width of theMζ-lines can be determined if the instrumenta profile is a Gaußian. Widths for Sr, Ru, Rh and Ag are presented for the first time.

     

Magnetostriction measurement by means of strain modulated ferromagnetic resonance (SMFMR)

A novel method for measuring magnetostriction constants is presented. A strain, periodic in time, applied to the sample, causes a modulation of the ferromagnetic resonance line position. The height of the signal obtained after phase-sensitive detection is proportional to the strain modulation depth. The appropriate magnetostriction constant λ is obtained by comparing the height of the SMFMR signal with that of the FMR line, as recorded by means of magnetic field modulation. Features of the new technique are:

1. high sensitivity: λ_min? 10_?9 forM=100 Oe and linewidth ΔH _d=1 Oe;
2. λ's belonging to distinct precession modes are separately determined;
3. applicable to thin layers for which strain gauge techniques cannot be used;
4. wide temperature range: 1.2 K<T<300 K;
5. uniform stress.

An illustrative example (YIG layer on GGG substrate) is given.     

Small-angle X-ray scattering on spinodal,nucleotic or coarsening processes in two-phase systems containing spherical,fibrillar or lamellar inhomogeneities

We study the effects of some of the most important and typical structural changes in two-phase systems on selected structural parameters obtained from small-angle x-ray scattering (SAXS) measurements. To limit the present study, it was assumed that the Phase, 1, embedded in the matrix

1. is monodispersed and homogeneous,
2. possesses one of the three most extreme shapes (spherical, fibrillar or lamellar) and
3. changes its behaviour

1. through type change (spinodal or nucleotic or coarsening), without changing the shape,
2. through a change of the shape only, or
3. through a) (type change) and b) (shape change) simultaneously.

To find the type of change for three basically different shapes of Phase 1 and to calculate its intensity (amount of the change) the following three SAXS parameters must be compared before and after the treatment of the system:

1. chord lengthl ₁ (and/or radius of gyrationR),
2. volume partw ₁ of the Phase 1, and
3. relative inner surfaceS _v of the system.

It is shown by this comparison that by the pure type change in the case of

1. spinodal change, all three SAXRS parameters are increasing or decreasing simultaneously and proportional to a power of the intensity of the change,
2. nucleotic change,l ₁ (and/orR) is unchanged, the other two (w ₁ andS _v ) are increasing or decreasing simultaneously and directly proportional to the intensity,
3. coarsening change,w ₁ is unchanged and anincreasing ofl ₁ is always accompanied by adecreasing ofS _v and vice versa.

In addition to this type change, the cases of mere changes of the shape (“shape change”) and finally of simultaneous type and/or shape change are studied. For the case of pure shape change the alteration of the dimensions (chord lengthl ₁ and/or radius of gyrationR) must be followed. The limitations of the analyses of the simultaneous type and/or shape change are discussed in detail.     

Bestimmung von Stoßfrequenz und Stoßmodell in verschiedenen Flammenplasmen aus Absorption und Dispersion von Mikrowellen

The electron collision frequencies for four flames of different temperature and composition have been determined by means of measuring simultaneouslyX-band microwave attenuation and phase shift, which originate from the complex conductivity of the flame plasma. Hence the method can also be used for the determination of the collision frequencies of time dependent plasmas. In order to enhance the small magnitude of the quantities to be measured one hundred equal flames burnt inside the waveguide. The measurements show:

1. In flames collisions of electrons with induced dipoles dominate (Lorentz-theory).
2. The collision frequencies depend on the flame temperatureand on the chemical composition.

     

New solid state fuel cells - green power source for 21st century

The exhaustion of the major fossil energy sources on earth in near future and the serious environmental pollution from the fuel combustion processes in the presently applied technologies are the most important problems of modern society. The sustainable development of mankind requests strongly to develop “green” power devices characterized by high fuel energy conversion efficiency, less pollution to the environment and convenience to use. Fuel cells have been commonly accepted to be a kind of clean, safe and convenient power source with high energy efficiency and are on the verge of revolutionizing the electric power industry by offering better ways to produce electricity and to deliver it to the consumers. Among all the advanced fuel cells being developed, which one might be the better choice for ideal green power generators in the 21st century? The answer is solid state fuel cells, particularly the solid oxide fuel cells(SOFCs) but not in the present stage of development. The new generation of SOFCs will certainly be based on all the results and experiences achieved so far in the fuel cell field and a lot of R & D work has to be performed furthermore. This paper attempts to present the current status of the R & D work on fuel cells, especially SOFCs, new concepts and trends, problems and possible measures which may initiate further discussion. The present article includes the following sub-topics:

The best electric power plants for the 21st Century

R & D on SOFCs: current status, problems and new trends

Intermediate temperature SOFCs - what do we need to do?

Fabrication techniques - soft chemistry routes

What to do for coming up with “green” power plants?

     

The moment of inertia at the saddle point of low energy fission of even-even nuclei

We use the molecular model of low energy fission, which describes the nucleus by two interacting fragments, to calculate the moment of inertia for U²³⁶ in the cranking approximation including BCS theory. We show that the moment of inertia at the saddle point:

1. depends almost linearly on the fragment distance.
2. is influenced only very weakly by the pairing constant and by the fragment deformations.
3. shows, as a function of the distribution of mass between the two fragments (A ₁ ,A ₂ ), a minimum near the magic configurationA ₁=132,Z ₁=50 and depends in this mass region strongly on the term structure near the Fermi energy.
4. is approximately that of a rigid body.

     

An investigation of the axial mode behaviour of a helical TEA-CO2 laser

The frequency behaviour of axial modes was investigated during the initial phase of mode competition in case of a helical TEA-CO₂ laser. With the help of a homodyne technique single-shot and multi-shot beat spectra were measured. Analysing these under various aspects and combining the results of an earlier investigation it was found that

1. inferior modes exist only for 100–200 ns.
2. their spectral width is less than 1 MHz and is determined by lifetime broadening, with the dominant mode narrower than 0.77 MHz,
3. in the average over many shots the spectral envelope of modes does not follow a Lorentzian shape as expected for the Lorentzian gain curve,
4. the beat powers change widely from shot to shot, whereas the total laser power remains constant,
5. no specific phase structures are likely to govern the laser emission, although the maximum emission principle appears to be obeyed with every individual shot. In an appendix relations are derived and summarized which are required for the evaluation of beat mode spectra and for the determination of line width as they apply to the actual time dependence of the laser emission.

     

Spin-order and magnetic properties of BaZn2Fe16O27 (Zn2-W) hexagonal ferrite

We have observed large peaks in the ultrasonic attenuation of a pure and two doped LaAl₂ crystals in the temperature region of about 45 K which are possibly of the Bordoni type. Their most interesting characteristics are:

1. There is only one peak in each sample.
2. The peaks are so narrow that they can be described by the original Seeger model with only one actication energy and one attempt frequency.

     

Versuche zum toroidalen Einschluß von Hoch-Beta-Plasmen mit Hilfe von helischen Multipolfeldern

Helical multipole fields with multiplicities of 1 to 3 and up to 16 field cycles around the circumference of the torus are superposed on a toroidal theta pinch. The vacuum fields of the configurations are calculated and regions of closed flux surfaces are found. The experimental results are:

1. Equilibria of High-Beta plasmas also exist, if the vacuum field has no absolute minimum, provided that the region of closed flux surfaces in the vacuum field has a greater diameter than the plasma, and that the helical multipole fields do not periodically increase and decrease the gradient of the toroidal main field. These equilibria are possibly unstable.
2. If the helical multipole fields periodically increase and decrease the gradient of the theta pinch field along the circumference of the torus there is no equilibrium, even if the helical curvature of the field lines is great.
3. The main cause of the losses is the escape of particles along the field lines.

     

Dynamical enhanced electron emission and discharges at contaminated surfaces

Broad-area electrodes show electron emission already at electric field strengthsF≈10⁷ V/m. This enhanced field emission (EFE) occurs only for contaminated surfaces. EFE is accompanied by photon emission and gas desorption yielding finally discharges. EFE is caused by dust and contaminants initiating the following effects:

an electron is stochastically emitted in a trigger zone

the electron gains energyΔE?eΔxF ^*

which excites electronic states

which relax by the emission of electrons, photons, and atoms

where the positive charges left behind enhanceF ^*=βF (β?1) initiating so an electron avalanche, i.e., a high conductivity channel. Because of charge migration and neutralization, this avalanche has a life time. This pulsating EFE is accompanied by light emission and gas desorption yielding finally a gas cloud and a discharge.

The pulsating, self-sustained EFE has the same root as:

the enhanced secondary emission found first by Malter

the conductivity switching exhibited by thin (≈ 1 μm) layers of semiconductors or insulators

the normal cathode fall and

the firing-wave instability in neurodynamics.

     

Existence of phase transitions for quantum lattice systems

We prove that the following lattice systems:

1. anisotropic Heisenberg model,
2. Ising model with transverse magnetic field,
3. quantum lattice gas with hard cores extending over nearest neighbours,

exhibit phase transitions if the temperature is sufficiently low and the transverse (or kinetic) part of the interaction sufficiently small.     

Infrared and conductivity studies on blends of PMMA/PEO based polymer electrolytes

Poly(methylmetacrylate)/poly(ethylene oxide) (PMMA/PEO) based polymer electrolytes were synthesized using the solution cast technique. Four systems of PMMA/PEO blends based polymer electrolytes films were investigated:

1. PMMA/PEO system,
2. PMMA/PEO + ethylene carbonate (EC) system,
3. PMMA/PEO + lithium hexafluorophosphate (LiPF₆) system and
4. PMMA/PEO + EC + LiPF₆ system.

The polymer electrolytes films were characterized by Impedance Spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The FTIR spectra show the complexation occurring between the polymers, plasticizer and lithium salt. The FTIR results give further insight in the conductivity enhancement of PMMA/PEO blends based polymer electrolytes.     

Magnetische und kalorische Eigenschaften von Alkali-Hyperoxid-Kristallen

The phase transitions of Alkali-Hyperoxide crystals (NaO₂, KO₂, RbO₂, and CsO₂) grown in liquid ammonia have been investigated by means of the following measurements:

1. magnetic susceptibility
2. differential magnetic susceptibility as magnetic field
3. magnetization curve in static and pulsed fields
4. specific heat.

The anomalies of the specific heat could be correlated with the magnetic properties and structural changes. Several new phase transitions were found. The magnetic behaviour of NaO₂ indicates magnetic order (of as yet unknown nature) at low temperatures. The magnetic and caloric behaviour of KO₂ at low temperatures is compatible with a Néel point at 7 K. A metamagnetic transition can be induced at temperatures below 12 K with fields of about 70 kOe. This transition is connected with structural changes. RbsO₂ and CO₂ are probably antiferromagnetic with Néel temperatures of 15 K and 9.6 K, respectively.     

Production spectrum of gamma rays in high energy interactions and high energy gamma ray intensity at 2900 m

An extended array of emulsion and lead plates has been exposed at Zugspitze for 6 months. The results of the measurements carried out on individual high energy cascades, and families of cascades allow the following conclusions to be drawn:

1. The vertical intensity of electrons andγ-quanta with energy > 1000 GeV on Zugspitze (2900 m) is 4.5/8.8 × 10^?10 cm^?2sec^?1ster^?1.
2. The energy spectrum of these particles has the shape of a power law with exponent — 1.85.
3. The production spectrum of secondary particles in individual interactions is derived, and it steepens with increasing primary energy. Using other evidence one may then conclude that this is due to an increase of multiplicity with primary energy.

     

Magnetic field and doppler velocity correlation in quiescent solar prominences

Analyzing statistically the magnetic and Doppler velocity data for 85 quiescent prominences observed in 1983–1987 by Nikolsky's magnetograph, we came to the following preliminary conclusions:

The average longitudinal magnetic field of the prominence determines the dynamic velocity of the latter: the stronger magnetic fields correspond to the higher Doppler velocities.

A longitudinal magnetic field less than 25 G allows the material to move with arbitrary velocity within the limits of several kilometers per second. A magnetic field higher than 25 G suppresses such movements.

The horizontal length of the flux tube exceeds its vertical part by 1.5 orders of magnitude (the upper limit).

There is an angle of 10°between the horizontal component of the velocity vector in quiescent prominences and the long axis of the filament.

The maximum velocity in quiescent prominences is about 7 km/s.

     

Strong cluster properties for classical systems with finite range interaction

In a previous paper, “strong” decrease properties of the truncated correlation functions, taking into account the separation of all particles with respect to each other, have been presented and discussed. In this paper, we prove these properties for finite range interactions in various situations, in particular

1. at low activity for lattice and continuous systems,
2. at arbitrary activity and high temperature for lattice systems,
3. at ReH≠0, β arbitrary and atH=0 for appropriate temperatures in the case of ferromagnets.

We also give some general results, in particular an equivalence, on the links between analyticity and strong cluster properties of the truncated correlation functions.     

Symmetrieeigenschaften achtkomponentiger Spinorfelder im Gitterraum

Starting from the four component Dirac equation for free particles without mass W.Heisenberg und W.Pauli have shown that the interaction term is uniquely defined, if one requires that all symmetries of free particles are preserved. Here we obtain similar results if we start from the eight component Dirac equation for free particles without mass:

1. The symmetry group of the eight component Dirac equation for free particles without mass has 16 parameters. It is isomorph to the direct product of the SU 4 and a one-parametric group: SU 4× (1).
2. The interaction operator is uniquely defined if one requires to preserve as many symmetries as possible of those given in (1).
3. But some of the symmetries in (1) are necessarily broken, in particular that of SU 3. The symmetry of the interaction operator is given by SO 4× (1)× (1).

These results mean:

1. The Heisenberg theory is uniquely defined, only if one assumes that the free particle part of the equation is well known.
2. The theory can be changed without modifying the fundamental idea ofHeisenberg andPauli to deduce an uniquely defined interaction operator if one starts with a modified free particle part.
3. A special kind of modification of the free particle part leads essentially to the SU 4-symmetry including that of SU 3, which is necessarily broken by the interaction term.
4. The question arises if this break of the SU 3-symmetry has something to do with the real break. This question is not yet touched in this paper.

     

Bounds on the number of eigenvalues of the Schrödinger operator

Inequalities on eigenvalues of the Schrödinger operator are re-examined in the case of spherically symmetric potentials. In particular, we obtain:

1. A connection between the moments of order (n ? 1)/2 of the eigenvalues of a one-dimensional problem and the total number of bound statesN _n, inn space dimensions;
2. optimal bounds on the total number of bound states below a given energy in one dimension;
3. alower bound onN ₂;
4. a self-contained proof of the inequality for α ≧ 0,n ≧ 3, leading to the optimalC ₀₄,C ₃;
5. solutions of non-linear variation equations which lead, forn ≧ 7, to counter examples to the conjecture thatC _0n is given either by the one-bound state case or by the classic limit; at the same time a conjecture on the nodal structure of the wave functions is disproved.

     

Stereological substructure analysis in hot-deformed metals from TEM-images

In the present paper three possible methods of stereological evaluation of particle arrangements are discussed:

determination of mean particle diameters by means of the so-called Poisson-Voronoi mosaics,

evaluation of the spatial particle-diameter distribution using the interception-length method of Spektor and

determination of the spatial distribution of grain or subgrain diameters on the basis of an intercept-area method of Saltykov.

Practical application of the procedures is demonstrated by results which were obtained from hot-deformation of several material under different hot-working conditions. It can be shown that stereological interpretation of TEM images renders refined conclusions concerning the mechanisms of structure changes occurring in hot-deformation.