Characterization of pulsed laser deposited chalcogenide thin layers

In this work we report on pulsed laser deposition (PLD) of chalcogenide thin films from the systems (AsSe)_100−xAgI_x and (AsSe)_100−xAg_x for sensing applications. A KrF* excimer laser (λ = 248 nm; τ_FWHM = 25 ns) was used to ablate the targets that had been prepared from the synthesised chalcogenide materials. The films were deposited in either vacuum (4 × 10⁻⁴ Pa) or argon (5 Pa) on silicon and glass substrates kept at room temperature. The basic properties of the films, including their morphology, topography, structure, and composition were characterised by complementary techniques. Investigations by X-ray diffraction (XRD) confirmed the amorphous nature of the films, as no strong diffraction reflections were found. The film composition was studied by energy dispersive X-ray (EDX) spectroscopy. The morphology of the films investigated by scanning electron microscopy (SEM), revealed a particulate-covered homogeneous surface, typical of PLD. Topographical analyses by atomic force microscopy (AFM) showed that the particulate size was slightly larger in Ar than in vacuum. The uniform surface areas were rather smooth, with root mean square (rms) roughness increasing up to several nanometers with the AgI or Ag doping. Based upon the results from the comprehensive investigation of the basic properties of the chalcogenide films prepared by PLD and their dependence on the process parameters, samples with appropriate sorption properties can be selected for possible applications in cantilever gas sensors.     

Method of local-scaling transformations and density functional theory in quantum chemistry. III. The energy density functional: Spin-restricted approach

The rigorous derivation of the energy density functional is proposed within the framework of the spinfree, or spin-restricted formulation of the energy density functional theory. It is shown particularly that the kinetic energy density functional is given by a sum of the Weizsacker term and the so-called “modified” Thomas–Fermi one. The variational principle is formulated for the energy density functional theory in terms of the Euler–Lagrange equation, and the virial theorem is proposed.     

Rapid structure determination of disordered materials: study of GeSe2 glass

X-ray diffraction experiments on GeSe₂ glass employing an Imaging Plate detector system have been carried out and their performance compared to that of traditional experiments employing point-type detectors. Imaging Plate detectors have been found to perform very well delivering good quality data for just a second. The analysis of the experimental data shows that the atomic ordering in GeSe₂ glass bears many of the characteristics of a random network of Ge-Se₄ tetrahedra.     

A rigorous energy density functional approach

A rigorous approach for constructing of energy density functionals is developed using the local-scale point transformation method. The exact kinetic energy density τ[ρ] contains two terms: the original Weizsäcker term τ_w[ρ] and a Thomas-Fermi-like term τ_w[ρ]. An energy density functionalE[ρ] is built up within a Slater determinant approximation using the most general Skyrme-type forces. It is demonstrated that all Hartree-Fock nuclear ground state results are reproduced quite accurately and consequentlyE[ρ] includes the shell effects accounted mostly by the particular form of τ[ρ]. The approach presented is compared with both Extended Thomas-Fermi and Expectation Value methods. Further possible applications are briefly considered.     

Structure of intercalated Cs in zeolite ITQ-4: an array of metal ions and correlated electrons confined in a pseudo-1D nanoporous host

The presence of Cs+ ions in the pseudo-1D nanopores of zeolite ITQ-4, Si32O64, is confirmed by x-ray diffraction and atomic pair distribution function analysis. Inside the nanopores the Cs+ ions are found to assemble in zigzag chains and thus form an extended, positively charged sublattice providing charge balance for a low-density electron gas also confined to the nanopores.     

Nucleon momentum and density distributions of nuclei

The time dependent Hartee-Fock-BCS code used to study¹¹⁸Pd+¹¹⁸Pd has been extended to study²³⁸U +²³⁸U at 7.5 MeV/A, in three dimensions, in order to look for the fission of the residual nuclei. Two impact parameters corresponding toL _in=150,300 ? are considered. 69 orbits are included in the effective charge quartet model. The energy loss and deflection angle are compatible with the available data and correspond to cases where fission of the residual system is observed experimentally. No fast fission of the final U fragment is predicted, but new details about clutching time, interaction times, dissipation times and other properties of the reaction mechanism such as neck dynamics, are obtained. No surface vibrations are seen.     

On the photochemical behaviour of ethyl acetoacetate in water

Irradiation of ethyl acetoacetate in water yielded acetic acid, ethyl acetate, acetonylacetone and diethyl succinate. The possible route of their formation is the recombination of the radicals resulting from the cleavage of the bonds between α-β and β-γ carbon atoms of the β-keto ester and/or their interaction with the solvent.     

Cosmic ray “knee” in the spectrum and proton-proton cross section from the point of view of new quarks

A possible explanation of the “knee” in the cosmic ray spectrum by the change in hadron-hadron interactions at the corresponding energy is discussed. It is shown that, at c.m. energies above 5 TeV, the total proton-proton cross sections obtained from cosmic ray experiments exceed the asymptotic fit made over the collider data. Such a rise of the cross sections favors the hypothesis about new chromodynamically charged degrees of freedom, the threshold of their creation being about \(\sqrt {^\mathcal{S} knee} \approx 2.3 TeV\). The properties of these new particles which are needed are discussed.     

Shape changes and test of the critical-point symmetry X(5) in N = 90 nuclei

Reliable and precise lifetimes of excited states in ¹⁵⁴Gd and ¹⁵⁶Dy were measured using the recoil distance Doppler shift (RDDS) technique. Excited states of ¹⁵⁴Gd were populated via Coulomb excitation with a ³²S beam at 110 MeV delivered by the FN tandem accelerator at the University of Cologne. For ¹⁵⁶Dy a coincidence plunger experiment was performed at the Laboratori Nazionali di Legnaro with the GASP spectrometer and the Cologne coincidence plunger apparatus using the reaction ¹²⁴Sn(³⁶S,4n)¹⁵⁶Dy at a beam energy of 155 MeV. Shape changes previously suggested to appear in the ground-state band (gsb) of ¹⁵⁶Dy and in the s-band above the first band crossing were not supported by the transition probabilities determined in this work. The measured transition probabilities of ¹⁵⁶Dy and ¹⁵⁴Gd as well as the corresponding energy spectra are compared with the predictions of the recently proposed X(5) model and in the case of ¹⁵⁶Dy also with an IBA fit.Received: 30 October 2002, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 27.70. + q - 21.60.Ev Collective models - 23.20.-g Electromagnetic transitions