Pressure–temperature phase diagrams for four higher members (nonyl–dodecyl) of the homologous series of 4′-alkyl-4-isothiocyanato-biphenyl ( n BT)

Differential thermal analysis (DTA) method was applied to study the pressure–temperature phase diagrams for four members of the 4′-alkyl-4-isothiocyanato-biphenyl (nBT) homologous series (n?=?9–12). These compounds exhibit a smectic E polymorphism enriched by a smectic A phase for two longest members. Measurements were performed in the temperature range 25–110°C and the pressure range up to 165?MPa. For all substances studied the pressure-induced phases were established with one or two triple points in the examined pressure range. In addition, for the 11BT and the 12BT the phases existing under atmospheric pressure disappeared under relatively low pressures. The results are compared with recently studied smectogenic n-alkyl-cyanobiphenyl (nCB) compounds.     

Theoretical study of molecular properties of low-lying electronic excited states of H2O and H2S

Geometries, excitation energies, dipole moments and dipole polarisability tensor components of the ground and four lowest excited states ³ B ₁, ¹ B ₁, ³ A ₂, ¹ A ₂ of the H₂O and H₂S molecules were calculated at the CASSCF, CASPT2, CCSD and CCSD(T) level of approximation. Vertical excitation and equilibrium transition energies of these states, having the Rydberg character, are reported too. Properties of both molecules in the ground and in low lying excited states are compared and discussed from the point of view of their molecular electronic structure. Upon excitation we observe dramatic changes of dipole moments and polarisabilities with respect to the ground state. We stress the change of the polarity of H₂O in all excited states accompanied by the enhancement of the dipole polarisability by an order of magnitude. Large, even if less pronounced, are changes of electric properties of H₂S in its excited states. Dipole moments and dipole polarisabilities of ³ B ₁, ¹ B ₁ states of H₂S and H₂O behave quite analogously in comparison to their respective ground state. The general pattern of properties for both molecules in their ³ A ₂ and ¹ A ₂ excited states is more different due to a pronounced participation of the sulphur d-orbitals in these states of the H₂S molecule.     

Formation and stability of Al-Mn quasicrystalline thin films prepared by high temperature successive deposition

This article reviews the results on the formation of i-QC thin films prepared by high-temperature successive deposition in the Al-Mn system and the metastable quasicrystalline Al₄Mn and crystalline Al₆Mn phase transformation in detail. Experimental evidence is given for the location of the solid-phase reaction. New data concerning the effects of preparation parameters (temperature, Mn deposition rate, composition) on the formation processes are reported. The phase formation and transformation processes are described by the combination of thermodynamic and kinetic factors.     

Existence and Homogenisation of Travelling Waves Bifurcating from Resonances of Reaction–Diffusion Equations in Periodic Media

The existence of travelling wave type solutions is studied for a scalar reaction diffusion equation in \(\mathbb {R}^2\) with a nonlinearity which depends periodically on the spatial variable. We treat the coefficient of the linear term as a parameter and we formulate the problem as an infinite spatial dynamical system. Using a centre manifold reduction we obtain a finite dimensional dynamical system on the centre manifold with fully degenerate linear part. By phase space analysis and Conley index methods we find conditions on the parameter and nonlinearity for the existence of travelling wave type solutions with particular wave speeds. The analysis provides an approach to the homogenisation problem as the period of the periodic dependence in the nonlinearity tends to zero.     

Investigation of the Three-Nucleon System Dynamics in the Deuteron–Proton Breakup Reaction

Precise and large sets of cross section, vector A _x , A _y and tensor A _xx , A _xy , A _yy analyzing power data for the ¹ H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A _xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations.     

A high-precision segmented Paul trap with minimized micromotion for an optical multiple-ion clock

We present a new setup to sympathetically cool ¹¹⁵In⁺ ions with ¹⁷²Yb⁺ for optical clock spectroscopy. A first prototype ion trap made of glass-reinforced thermoset laminates was built, based on a design that minimizes axial micromotion and offers full control of the ion dynamics in all three dimensions. We detail the trap manufacturing process and the characterization of micromotion in this trap. A calibration of the photon-correlation spectroscopy technique demonstrates a resolution of 1.1 nm in motional amplitude of our measurements. With this method, we demonstrate a sensitivity to systematic clock shifts due to excess micromotion of $|(\Updelta\nu/\nu)_{\rm mm}|=7.7\times10^{-20}$ along the direction of the spectroscopy laser beam. Owing to our on-board filter electronics on the ion trap chips, no rf phase shifts could be resolved at this level. We measured rf fields over a range of 400 μm along the ion trap axis and demonstrated a region of 70 μm where an optical frequency standard with a fractional inaccuracy of ≤1 × 10^?18 due to micromotion can be operated.     

Uniform nanoparticles by flame-assisted spray pyrolysis (FASP) of low cost precursors

A new flame-assisted spray pyrolysis (FASP) reactor design is presented, which allows the use of inexpensive precursors and solvents (e.g., ethanol) for synthesis of nanoparticles (10–20 nm) with uniform characteristics. In this reactor design, a gas-assisted atomizer generates the precursor solution spray that is mixed and combusted with externally fed inexpensive fuel gases (acetylene or methane) at a defined height above the atomizing nozzle. The gaseous fuel feed can be varied to control the combustion enthalpy content of the flame and onset of particle formation. This way, the enthalpy density of the flame is decoupled from the precursor solution composition. Low enthalpy content precursor solutions are prone to synthesis of non-uniform particles (e.g., bimodal particle size distribution) by standard flame spray pyrolysis (FSP) processes. For example, metal nitrates in ethanol typically produce nanosized particles by gas-to-particle conversion along with larger particles by droplet-to-particle conversion. The present FASP design facilitates the use of such low enthalpy precursor solutions for synthesis of homogeneous nanopowders by increasing the combustion enthalpy density of the flame with low-cost, gaseous fuels. The effect of flame enthalpy density on product properties in the FASP configuration is explored by the example of Bi₂O₃ nanoparticles produced from bismuth nitrate in ethanol. Product powders were characterized by nitrogen adsorption, X-ray diffraction, X-ray disk centrifuge, and transmission electron microscopy. Homogeneous Bi₂O₃ nanopowders were produced both by increasing the gaseous fuel content and, most notably, by cutting the air entrainment prior to ignition of the spray.     

Polyhalogen and Polyinterhalogen Anions from Fluorine to Iodine

This Review deals with the evolving field of polyhalogen chemistry, specifically polyhalogen anions (polyhalides). In addition to a historical outline, current progress in synthetic approaches towards the formation of polyfluorides, polychlorides, polybromides, and polyinterhalides is also illustrated. The structural diversity of polyhalides has substantially increased in the past decade, especially for polychlorides and polybromides, which are commonly characterized by single‐crystal X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations. Polyfluorides have been examined by sophisticated state‐of‐the‐art quantum‐chemical calculations and investigated spectroscopically in noble gas matrix‐isolation experiments under cryogenic conditions at 4 K. The bonding in such polyhalide systems is also discussed. The last Section deals with applications of polyhalides in halogenation reactions and electrochemistry as well as their use as reactive ionic liquids, emphasizing the promising future of polyhalogen chemistry.