Ab initio MO study of the potential energy surface of the N2…C1F binary complex

The potential energy surface for the complex between the N₂ and C1F monomer units was investigated comprehensively at the SCF/4-31G level. A minimum-energy plane is shown by a contour plot. The surface consists of 606 individual computed points which, by symmetry, give a surface of 1296 points. Several maxima and minima are readily identified. These structures were investigated using the STO/6-31+G** basis set at the self-consistent field level, and using the MP2/6-31+G^** basis set to include electron correlation effects. The nuclear quadrupole coupling constant and the asymmetry parameter for the nitrogen atoms in the various structures are reported.     

Glueball mass spectrum and mass splitting in 2+1 strongly coupled lattice gauge theories

For a 2+1 strongly coupled (β=2/g ² small) Wilson action lattice gauge theory with complex character we analyze the mass spectrum of the associated quantum field theory restricted to the subspace generated by the plaquette function and its complex conjugate. It is shown that there is at least one but not more than two isolated masses and each mass admits a representation of the formm(β)=?4lnβ+r(β), wherer(β) is a gauge group representation dependent function analytic inβ ^1/2 orβ atβ=0. For the gauge group SU(3) there is mass splitting and the two massesm _± are given by $$m_ \pm (\beta ) = - 41n\beta + 16r^4 + \tfrac{1}{2}(2 \pm 1)\beta + \left( {d_ \pm (\beta )\sum\limits_{n = 2}^\infty {c_n^ \pm } \beta ^n } \right)$$ wherer=3 is the dimension of the representation andd _±(β) is analytic atβ=0.c _n ^± can be determined from a finite number of theβ=0 Taylor series coefficients of finite lattice truncated plaquette-plaquette correlation function at a finite number of points.     

On the classical behavior, coherent and incoherent contributions to scattering of atoms from a surface

In this work we calculate the coherent and incoherent contributions to the diffraction probability of atoms scattered by a surface. We are interested in exploring the relative importance of each of these contributions, and compare them with results obtained from molecular dynamics calculations. To achieve this goal, we employed a method developed by Heller that consists of writing the incident plane wave as a sum of Gaussian wave packets, propagating them independently by using the time dependent Schrödinger equation, and constructing the scattered wave function by adding coherently the scattered packets. For the system studied, the molecular dynamics results show the largest intensity in the specular region and also display a classical rainbow structure. On the other hand, the quantum results exhibit diffraction features, with the coherent contribution accounting for most of the total intensity probability.     

Hydrothermal synthesis and structural characterization of a novel cadmium-organic framework

A three-dimensional diamondoid cadmium-organic framework, formulated as [Cd(NDC)(H₂O)] (I) (where NDC²⁻=2,6-naphtalenedicarboxylate), has been hydrothermally synthesized and structurally characterized using single-crystal X-ray diffraction. The hydrothermal synthesis of I has been optimized by modifying the composition of the reactive mixture and the temperature programme, so that a highly crystalline and pure homogeneous phase could be obtained. A novel layered structure, formulated as [Cd₂(NDC)(OH)₂], was isolated when the molar ratio of triethylamine exceeds ca. 0.7. Both products have been characterized using powder X-ray diffraction, IR and Raman spectroscopies, and elemental and thermal analyses.     

Experimentelle Grundlage zur Bestimmung des Wasserstoffions durch Farbanalyse

Zusammenfassung Es wurde eine experimentelle Grundlage zur farbanalytischen Bestimmung des Wasserstoffions folgendermaßen aufgestellt:Mit Hilfe des Veronal-Acetat-Puffers vonL. Michaelis wurde eine Reihe von Pufferlösungen dargestellt, entsprechend den Umschlaggebieten der Originalindikatoren vonW. M. Clark undH. A. Lubs (Bromphenolblau, Bromkresolpurpur, Bromthymolblau, Phenolrot, Kresolrot und Thymolblau). Jede Lösung wurde mit dem betreffenden Indikator versetzt und die entstandene Farbe unter drei Farbfiltern (Rot, Grün, Blau) und unter Anwendung einer Barytweißplatte als Normale mit dem Stufenphotometer vonC. Pulfrich nach der Methode vonE. Haschek undM. Haitinger photometriert. Die Bestimmungsstücke jeder Farbe sind mit Hilfe der Formeln vonA. G. de Almeida (für Sättigung und Farbton) undF. Exner (für Helligkeit) berechnet worden. Dann wurden für jeden Indikator dieph-Werte als Abszisse und die Farbtonwerte als Ordinate in einem System von zwei rechtwinkligen Achsen aufgetragen und die Resultate ergaben S-förmige Kurven, deren Gleichung abgeleitet wurde.Die Resultate zeigen, daß dem Farbtonunterschiede von = 0,0006 (ungefähr äquivalent 1 Å-Einheit) einph-Unterschied von 2 bis 4 Tausendsteln entspricht, was eine Genauigkeit darstellt, die mit der elektrometrischen Methode nicht erreichbar ist.Diese Arbeit war ebenso wie die vorhergehende für den 25. Band der Mikrochemic bestimmt, kann jedoch aus technischen Gründen erst im vorliegenden Heft veröffentlicht werden. Sie wurde noch von der früheren Schriftleitung der Mikrochemie redigiert.     

Crystallization Behavior of SiO2-TiO2 Sol-Gel Thin Films

The aim of this work was to investigate the crystallization behavior of thin films of SiO₂−TiO₂ made by the sol-gel process as function of the TiO₂ content and the temperature and time of heat treatment. Precursor solutions were prepared by hydrolysis of TEOS (tetraethoxysilane) and TPOT (titaniums tetraisopropoxide). Multilayer films were spun on single crystal silicon wafers. The compositions studied were (on a molar percentage basis) 20TiO₂−80SiO₂, 30TiO₂−70SiO₂, 40TiO₂−60SiO₂ and pure TiO₂. The films were heat treated at different temperatures between 300°C and 1200°C, for different periods of time (30 s-90 h). The crystallization kinetics were followed by micro-Raman spectrometry. Grazing incidence X-ray diffraction showed that the films crystallized into one or both of two crystalline phase of TiO₂: anatase and rutile (for pure TiO₂ only). The volume fractions of the crystalline phase varied from very low values (<1%), up to 100%, for a TiO₂ sample heat treated at 800°C for 8 hours. The results show that the volume fraction of crystalline phase is strongly influenced by the heat treatment temperature and also, to a smaller extent, by the heat treatment time. The most important parameter, however, is the composition of the films: the higher their TiO₂ concentration, the lower is the crystallization temperature and the larger is the crystallized fraction.     

Er photoluminescence enhancement in Ag-doped sol-gel planar waveguides

This paper reports on the study of the effects of silver (Ag^o) nanoparticles on the optical and spectroscopic properties of Er³⁺-doped silica-based gels and glasses, including active bulk materials and planar waveguides for integrated optics. Two different procedures for silver and erbium ion incorporation into the glassy matrices have been investigated: the direct incorporation of a metal salt (AgNO₃ and/or Er(NO₃)₃) into the sol-gel solution, as well as a modified sol-gel process, based on pore-doping of a precursor gel with AgNO₃ and/or Er(NO₃)₃ solutions. The study of the parameters determining the average size and size distribution of the nanoparticles, together with their influence on the sol-gel material densification and Er³⁺ photoluminescence at 1.5 μm, has been performed by means of transmission electron microscopy, plus ultra-violet/visible and photoluminescence spectroscopies. The Ag^o colloidal nanoparticles, obtained by thermal precipitation, were approximately spherical, homogeneously distributed and they exhibited an average size between ∼2 and 15 nm, depending on the silver content and heat treatment performed. They are shown to be responsible for a remarkable enhancement of the Er³⁺ photoluminescence intensity, which is mainly due to the increase of the local electric field around the Er³⁺ ions, due to the surface plasmon resonance of the Ag^o nanoparticles.     

Vibrational spectra and structure of chloro-fluorozirconate glasses

A series of barium chloro-fluorozirconate glasses have been prepared. Their IR absorption, IR reflectivity and Raman spectra have been measured down to 33 cm^?1. The glass transition and crystallization temperatures have also been measured. The high frequency IR absorption and Raman modes of the chloro-fluorozirconate glasses have been assigned as in fluorozirconate glasses. The IR reflection spectra of chloride-containing glasses differed from the fluorozirconates in that one band was clearly related to Cl atom motions. The structure of the glasses probably consists of zig-zag chains of ZrCl₂F₄ mixed halide octahedra plus a pure fluoride matrix whose structure is similar to that of a ZrF₄BaF₂ glass with the same composition.