Highly oriented thin oxide films on single crystals of Fe-Si alloys

Under certain oxidation conditions, highly oriented oxide films grow on single crystals of some Fe-Si alloys. A typical two-phase film of this kind was studied in order to reveal the orientational relationships between-Fe₂O₃ and Fe₃O₄ on the (001) surface of the substrate. The orientational relationships were determined from reflection high-energy electron diffraction patterns where reflections from both oxides were present.The authors are indebted to Ing. B. esták and Ing. S. Kadeková who made possible the preparation of single-crystalline samples of Fe-Si alloys in the Institute of Physics, Czechoslovak Academy of Sciences; to Dr. M. Rozsíval (Institute of Solid State Physics, Czechoslovak Academy of Sciences) who enabled the authors to use the electron diffraction apparatus; and to Dr. A. Línek (Institute of Solid State Physics, Czechoslovak Academy of Sciences) for helpful discussion.     

Wavelength distribution of X-rays in the focus of a monochromator and an estimate of the influence of this distribution on precision measurements of lattice constants

Wavelength distribution in the focus of a Johansson type monochromator is computed assuming the tube focus emissivityG(), reflection curveR() and wavelength distribution of the incident radiationJ(-₀) are known. It is shown e.g. that the centre of gravity may be shifted in accordance with the position of the crystal on the focal circle which may considerably influence precision measurements of lattice parameters.

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, G(,) R() J(-₀) . , , , .

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The author is grateful to Z. Hemanová for carrying out all the computations very carefully.     

ИНТЕРФЕРЕНЦИЯ ДВУХ Э СТЕСТВЕННYХ ПУЧКОВ СВ ЕТА, ПРОШЕДШИХ ЧЕРЕЗ ОПТИ ЧЕСКИ АКТИВНУЮ) СРЕДУ

, .     

On the massive sine-Gordon equation in all regions of collapse

The ultraviolet stability for the cosine interaction in two dimensions and finite volume is rederived for values ² [4, 32/5[ and proven for the remaining ² [4, 8[ by using renormalization group methods developed in [G, GN1] to portray renormalized effective potentials arising from a multiscale decomposition.Supported by the Studienstiftung des Deutschen VolkesSupported in part by the Schweizerischer Nationalfonds     

A complete proof of the Feigenbaum conjectures

The Feigenbaum phenomenon is studied by analyzing an extended renormalization group map . This map acts on functions that are jointly analytic in a position variable (t) and in the parameter () that controls the period doubling phenomenon. A fixed point ^* for this map is found. The usual renormalization group doubling operatorN acts on this function ^* simply by multiplication of with the universal Feigenbaum ratio ^*= 4.669201..., i.e., (N ^*(,t)= ^*( ^* ,t). Therefore, the one-parameter family of functions, ^* , ^* (t)=( ^*(,t), is invariant underN. In particular, the function ₀ ^* is the Feigenbaum fixed point ofN, while ^* represents the unstable manifold ofN. It is proven that this unstable manifold crosses the manifold of functions with superstable period two transversally.     

Vector meson production and [SU(3) ⊗SU(3)]coll symmetry

The collinear production of a vector meson is considered in the scattering of pseudoscalar mesons on baryons. Relations between the experimental quantities, following from the symmetry [SU(3) SU(3)]_coll, are obtained.On leave from the Nuclear Research Institute of the Czechoslovak Academy of Sciences, e.     

Optical Thin-Film Sensors for the Determination of Aqueous Halide Ions

Fourteen thin-film optical sensors in which halide-sensitive fluorophores are immobilized in a thin copolymer film (50 m, dry) have been developed and characterized. The sensor films use rhodamine, 6-methoxyquinoline, and harmane dyes which have been functionalized and bound to a hydrophilic copolymer. The sensor films are reversibly capable of determining aqueous bromide and iodide with 4 and 2% accuracy, respectively, at concentrations of around 10^–3 mol dm^–3, and are more sensitive than previous plastic sensor fabrications. The 90% response time to molar iodide is 30–60 s. A combination of sensor films allows the simultaneous determination of both I^– and Br^– in a mixed-halide solution. The interference of several ions, including pseudo-halides, on the sensor films has been studied.     

Electron states of manganese luminescence centres in A1N

The energy spectrum of manganese luminescence centres in AlN was studied by means of excitation and emission spectra. Two regions of excitation were found: in the first region (from 40 000 to 31 000 cm^–1) excitation occurs as a result of transfer of energy from other impurity centres to the manganese centres; in the second region (from 26 000 to 17 000 cm^–1) the manganese centres are excited directly. In the excitation band with a peak at about 19 200 cm^–1 a phonon structure was observed having a temperature dependence analogous to that of the phonon structure of the emission band. The phonon energy at excitation differs from that at emission (_exc260 cm^–1, _em160 cm^–1). A scheme of electron-phonon levels of manganese centres in AlN is presented, and problems relating to the structure of these centres are discussed.Na Slovance 2, Praha 8, Czechoslovakia.The authors would like to thank Dr. L. Kratina and Dr. F. Kubec (Institute of Radio Engineering and Electronics, Czechoslovak Academy of Sciences), who kindly performed the EPR measurements, and to Professor M. Trlifaj and Dr. J. Pastrák for valuable discussions.     

Raman effect of light on argon atoms

Scalar scattering of light on the 3p and 3s subshells of the argon atom (Stokes scattering) and anti-Stokes scattering on the excited 4p and 4s states of argon are examined in the Hartree-Fock approximation. The calculation is made in a velocity form and in a length form. It is shown that the value in the r form is 1.5–2 times greater than in the form.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 36–42, January, 1977.     

On X-ray measurements of residual stresses in materials with lattice strain gradient

The non-linear distribution of lattice strain ³¹⁰vs sin² observed on the surface of a polished steel specimen can be interpreted by tri-axial stress state with surface components of stress tensor ₁₁(0)= ₂₂(0) and gradientsg ₁₁= ₁₁/T, g ₃₃= ₃₃/T. The distribution of experimental values is duscussed from the viewpoint of various ways of calculating ₁₁.The authors would like to thank Dr. J. Musil, D. Sc. of the Institute of Physics of Czechoslovak Academy of Sciences for kindly providing the samples which made possible this study.     

On existence of a bound state in an L-shaped waveguide

We investigate the Laplace operator in an L-shaped strip of a widthd with Dirichlet boundary conditions. It is shown that it has a unique eigenvalue corresponding to a square-integrable eigenfunction, namely = 0·93 (/d)². This result has implications for the theory of waveguides as well as for electron motion in some microscopic semiconductor devices.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.On leave of absence from Nuclear Physics Institute, Czechoslovak Academy of Sciences,250 68 e near Prague, Czechoslovakia.On leave of absence fromDepartment of Mathematics, Faculty of Nuclear and Technical Engineering, Czech Technical University, Trojanova 13, 120 00 Prague, Czechoslovakia.     

Te-waves guided by arbitrary nonlinear dielectrics bounded by linear media

Considerable interest is currently being devoted to nonlinear propagation in dielectric slab waveguides for integrated optics and millimetric applications. Much of the current work is based on Kerr-like ( E ²) nonlinear media and numerically discussed. We present a exact solution of TE-waves for arbitrary nonlinear dielectric ( |E| ). We applicate this solution to the planar nonlinear optic waveguides and the dispersion relations are given. The results show that the propagation constants are a function of the field magnitude.Supported by deutscher akademischer austauschdienst (DAAD)He is now with Dept. Electrical Engineering, Duisburg University, 4100 Duisburg, Germany     

Simulation of emission and absorption spectra of a laser-produced plasma

Conclusion The ideas developed suggest the feasibility of developing a radiative gasdynamics program that takes into account, selfconsistently and without contradictions, the dependence of the material characteristics (arbitrarily detailed, in principle) for an optically transparent and an opaque plasma. It is necessary to assess beforehand the influence of the method used to choose () in Eqs. (15)–(17). One more research trend may involve the possibility of finding conditions with inverted population in the x-ray band not on the basis of the kinetics of the transitions, but on the basis of equilibrium characteristics of the ions in a plasma with time-varying conditions.Lebedev Institute, Russian Academy of Sciences, Moscow. Keldysh Institute, Russian Academy of Sciences, Moscow.     

Traffic Jams in a Lattice-Gas Model

We propose a simple lattice-gas model characterized by two states of atoms, the thermalized state, which is the same as in the standard lattice-gas model, and the running state, where the atoms jump in one direction only. The model exhibits the existence of traffice jams (bunching of thermalized atoms in compact groups), the nonlinear dependence of mobility on the jump probability, and the hysteresis.     

Production of supersymmetric particles ine + e − andep collisions

A review is given of the theoretical predictions for chargino, neutralino and selectron pair production ine ⁺ e ^– annihilation and for slepton and squark production inep collisions. The energy range considered is that of LEP, SLC and HERA. The expectations for the production of SUSY particles at ane ⁺ ev ^– collider in the TeV energy range are also discussed.Invited talk at the International Symposium Hadron Interactions — Theory and Phenomenology, Bechyn, Czechoslovakia, June 26–July 1, 1988.I want to thank H. Baer, H. Fraas, D. Karatas, W. Majerotto and X. Tata for discussions and correspondence. Financial supports of the Czechoslovak Academy of Sciences and the Austrian Academy of Sciences are gratefully acknowledged.     

Surface damage in single-crystal Mn-Zn ferrite

The depth of the damaged surface layer and the changes of hysteresis loop caused by surface processing in Mn_0.53Zn_0.35Fe_2.12O₄ single crystal are measured. The results obtained are treated as a consequence of the crystal structure deformation at the surface and coherent limited domain wall movement.Dedicated to Dr. Svatopluk Krupika on the occasion of his 65th birthday.The author would like to thank Dr. Z. ima, Institute of Physics, Czechoslovak Academy of Sciences, for valuable discussions.     

Double N-N scattering on polarized proton target

The triple scattering depolarization transfer parameterD _t in elastic p-p scattering was measured at an energy of 660 MeV using a polarzied proton target. All measurements have been carried out with the help of an optical spark chamber.The following results have been obtained:D _t (90)=D(90)=0·54±0·10.D _t (130)=D(130)=0·72±0·11.Devoted to Professor V. Petrílka on his sixty-fifth birthday.On leave of absence from theInstitute for Computing Technique of the Czechoslovak Academy of Sciences, Prague.On leave of absence from theNuclear Research Institute of the Czechoslovak Academy of Sciences, e.On leave of absence from theFaculty of Nuclear Science and Physical Engineering of the Technical University, Prague.In conclusion the authors express their deep gratitude to S. M. Bilenky, G. Gozzika, M. Hansroul, L. Lapidus, M. Odehnal, M. Maly, B. S. Neganov, R. M. Ryndin and P. Winternitz for helpful discussions and J. Cechová, E. Dudová and H. Sternová for help in the work.     

Dispersion relations for forward pion-pion scattering and their consistency with Wolf pion-pion phase shifts

It is shown that the Wolf pion-pion phase shifts are in reasonable agreement with dispersion relations for forward scattering. The extent to which the inaccuracies of the experimental data might modify this agreement is examined.At attempt is made to explain some discrepancies which arise probably from too broad a -meson peak.The author is indebted to Dr. M. Petrá for valuable discussions, to P. Bóna for help with some calculations and to Dr. J. Mikloko from the Computing Centre of the Slovak Academy of Sciences for programming and computation. He is also indebted to Dr. G. Wolf and to Dr. F. Meiere for sending a copy of their papers prior to publication.     

The lifetime of the “ferroelectric” phonon in some perovskite crystals at low temperatures

The lifetime of a low-lying transverse optic phonon with the wave vectork=0 (ferroelectric phonon) in perovskite crystals having the Curie point at low temperatures is investigated. Using a phenomenological Hamiltonian it is shown that mainly the process, in which the ferroelectric phonon and the transverse acoustic phonon are destroyed in order to create another optic phonon from the same branch, determines the lifetime of a ferroelectric phonon. The general result is specialized for SrTiO₃, and the temperature dependence of, exhibiting anomalies in comparison with normal ionic crystals, is discussed.The author thanks Dr. M. Marvan of the Physical Faculty of Charles University in Prague and Dr. P. Glogar and Dr. M. Trlifaj of the Institute of Physics, Czechoslovak Academy of Sciences, in Prague for valuable remarks.