Diffraction of fast metastable atoms by micrometric reflection gratings

Diffraction of thermal velocity metastable atoms by non-magnetic and magnetic reflection gratings of micrometric period has been observed. This observation is made possible by the use of an ultra narrow beam generated by metastability exchange. Grazing incidence angles are exploited to minimise the quenching of metastable atoms on the grating surface. Potential applications are beam splitting, atom holography and probing of micro-sized solid surfaces.     

Schlieren imaging of nano-scale atom-surface inelastic transition using a Fresnel biprism atom interferometer

Surface-induced exo-energetic inelastic transitions among atomic Zeeman states in a magnetic field (“van der Waals – Zeeman” transitions) are useable as tuneable beam splitters. A transversally coherent atom beam impinging a pair of opposite surfaces (e.g. 2 edges of a slit or of an ensemble of periodic slits) gives rise to two coherently diffracted wave packets. Within the wave packet overlap, non-localised interference fringes of the Young-slit type are predicted. From the diffraction pattern observed in the Fraunhofer regime (Schlieren image), detailed information about the transition amplitude on a scale of a few nanometers should be derived.     

Optical characterization of As2Se3-Ag4SSe-SnTe amorphous thin films

Amorphous thin films from the system As₂Se₃-Ag₄SSe-SnTe were prepared by thermal vacuum evaporation from the corresponding bulk glassy samples. The film structure and surface morphology were investigated by scanning electron microscopy and atomic force microscopy; the results revealed uniform, smooth and homogeneous coatings. The amorphous chalcogenide films are transparent in a wide spectral range as shown by transmission and reflection measurements in the VIS and NIR regions. The optical band gap was determined and its compositional dependence is discussed in terms of structural considerations and the formation of charged defect centers.     

Phase equilibria in the Ag2Te-Cd system

The phase diagram of the Ag₂Te-Cd system, which is a polythermal section of the ternary system Ag-Cd-Te, was established by means of DTA and metallographic analysis. The diagram contains 32 phase regions, including the polymorphic modifications of Ag₂Te, solid solutions based on Ag₂Te and Cd, and two intermediate phases with variable compositions: Ag₂Cd_1+xTe and Ag₂Cd_5+xTe.

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Zusammenfassung Das Phasendiagramm des Systems Ag₂Te-Cd, eines polythermen Schnittes im ternären System Ag-Cd-Te, wurde aus DTA- und metallographischen Ergebnissen konstruiert. Das System besteht aus 32 Ein- und Zweistoffgebieten, darunter den polymorphen Modifikationen des Ag₂Te, festen Lösungen auf Basis Ag₂Te bzw. Cd, und ternären Phasen mit den variablen Zusammensetzungen Ag₂Cd_1+xTe und Ag₂Cd_5+xTe.

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Ag₂Te-Cd, AgCd-. , Ag₂Te, Ag₂Te Cd, Ag₂Cd_1+x Te Ag₂Cd_5+x Te.

     

Phase equilibria in the Ag2Te-ZnTe and Ag2Te-Zn systems

The state diagrams (T-x) of the systems Ag₂Te-ZnTe(I) and Ag₂Te-Zn(II) are offered on the ground of data obtained by differential thermal analysis, X-ray phase analysis, microstructural analysis and measurements of the density and the microhardness of samples synthesized. The systems studied are quasibinary sections of the ternary system Ag-Zn-Te. System I is characterized by two eutectic and three eutectoidal non-variant equilibria as well as by an intermediate compound Ag₂ZnTe₂, which melts congruently at 880°C. The latter exists in the range from 120 to 880°C in two polymorphic modifications (T_ʅ→β=515°C). System II is characterized by one eutectic, two eutectoidal and one peritectic nonvariant equilibria, boundary solid solutions on the ground of Ag₂Te and Zn and one intermediate phase of the composition Ag₄Zn₃Te₂, which melts congruently at 880°C.     

Complex forming properties of crosslinked poly (ethylene oxide). I. Interaction of linear and crosslinked poly(ethylene oxide) with molybdenum(vi) salts

Evidence was found of donor–acceptor complexation of molybdenum(VI) compounds by linear and crosslinked PEO. The interaction was studied by optical and NMR spectroscopy and conductivity measurements in organic medium. PEO networks were capable of binding molybdenum salts even in aqueous solution. The character of the interaction is considered to be essentially different from complex formation with alkali metal salts. This is manifested in the relatively low values of the stability constants of complexes with linear PEO. A remarkable effect of crosslinking on the binding capacity of PEO is registered resulting in an increase of complexation constants in chloroform by two orders of magnitude.     

A combined photoacoustic DSC for simultaneous temperature modulated measurements: does it really work?

Combination of two techniques, photoacoustic (PA) and differential scanning calorimetry (DSC), is a combination of quasi stationary thermodynamic DSC method and nonstationary dynamic PA method. Especially favorable and easy to realize is the combination with power compensated type of DSC. It has several advantages over the use of two techniques separately and allow to perform measurements simultaneously. The most obvious is simultaneous determination of thermodynamic properties such as specific heat, heat of transition and dynamic properties such as effusivity, thermal conductivity at the different phase transitions and complex specific heat at the glass transition. Unlike other temperature modulated techniques PA–DSC is especially suitable for studying polymer materials since their low thermal conductivity is an additional advantage. Conditions for simultaneous measurements are examined. It is proved that the combination of two techniques and necessary changes in construction do not essentially change adequate work of the instrument. A little disbalance of DSC operation due to the construction change can be corrected simply by recalibration. The procedures for testing and calibration for the proper operation of the combined PA–DSC are given together with some details of experimental methodology. Several measurements could serve as examples of widespread applicability of PA–DSC to study different types of phase transitions as well as time dependent processes such as glass transition.     

Diffusion couple studies of the Ti‐Bi‐Zn system

The system Ti‐Bi‐Zn has been investigated using diffusion couples consisting of solid Ti and liquid (Bi+Zn) phase. The diffusion paths at 400, 500, 700 and 800 °C have been traced by means of electron microprobe analyses. The growth constants of the diffusion layers are roughly assessed. The phase diagram data obtained in this investigation are compared with previous studies of equilibrated alloys. The existence of the ternary compound TiBiZn has been confirmed. The formation of another phase with approximate formulae Ti₄Bi₃Zn to Ti₉Bi₇Zn₄ has been observed at high temperatures. The latter compound as well as the ternary extension of the Ti_XBi_Y (X ≈ 5, Y ≈ 6) phase react easily with air. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contribution to the Ti‐Bi phase diagram

The system Ti‐Bi has been investigated by solid/liquid diffusion couples at 400, 500, 600 and 700 °C. Indication that the growth rate of the diffusion layers at 500 °C is linear has been found, with a growth constant of around 5 × 10^–11 m.s^–1. The existence of the Ti₂Bi phase has been confirmed. Some formerly unknown binary phases (TiBi, Ti₂Bi₃, TiBi₂) have been observed. The phase TiBi is, probably, identical with Ti₈Bi₉ reported previously. All intermediate phases suffer air corrosion, but in various degrees. A tentative variant of the Ti‐Bi phase diagram, including the newly found compounds, has been constructed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)