Study of nitrate radical (NO3) reactions with carbonyls and acids in aqueous solution as a function of temperature

Using laser photolysis experiments, the reactivity of the nitrate radical towards four carbonyl compounds and three carboxylic acids was studied. All kinetics measurements were carried out as a function of the temperature in the range from 278 K to 318 K. Furthermore, the effect of the acid-base equilibrium on the reactivity of the three acids was studied by measuring the activation parameters of the dissociated and undissociated acids at pH = 6 and pH = 0.5, respectively. The following Arrhenius expressions were obtained: [Formulas: see text]. Errors stated throughout this study are statistical errors for a confidence interval of 95%. The importance of the obtained results for the understanding of the tropospheric oxidation processes is discussed. The kinetics resulting from this work are compared with results for other atmospheric radicals.     

Synthesis and structure of novel copper(II) complexes with pyrazole derived ligands and metal–ligand interaction in solution

Two new ligands of the coumarin type have been synthesized and characterized by ¹H, ¹³C NMR, IR and MS. The crystal and molecular structures of ligand 2, determined by the X-ray diffraction method, are presented. With copper(II) these ligands create solid complexes of the type CuLCl₂, where L is 5-(2-hydroxybenzoyl)-3-methyl-1-(2-pyridinyl)pyrazol-4-carboxylic acid methyl ester (2) or 3-methyl-1-(2-pyridinyl)-1H-chromene[4,3-c]pyrazol-4-on (3). The new copper(II) complexes have been characterized by elemental analysis and solid state FT-IR. The protonation constants of ligands 2 and 3 have been determined in 5% v/v 1,4-dioxane–water solution (25 °C). The coordination modes in the complexes with copper(II) are discussed for 2 on the basis of potentiometric and UV–Vis data.     

Interaction of alkali metals with perylene-3,4,9,10-tetracarboxylic-dianhydride thin films studied by IR spectroscopy

In order to clarify the doping behavior of different alkali metals in perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), Fourier transform infrared spectra of PTCDA thin films doped with sodium, potassium, and cesium were measured and compared. Furthermore the vibrational properties were calculated using density-functional theory and these calculated vibrational frequencies were assigned to the experimental IR modes of the thin films.     

Prompt light particle emission in the 36Ar + 58Ni reaction at 95 MeV/nucleon

The prompt component at intermediate velocity of light charged particles is investigated. An improved coalescence model coupled to the intra-nuclear cascade code ISABEL is used to obtain light complex particle energy spectra and multiplicities as a function of impact parameter. The results are compared with experimental data from the ³⁶Ar + ⁵⁸Ni experiment at 95 MeV/nucleon, performed with the INDRA 4π detection system. The calculated prompt component is found to rather well reproduce proton spectra. For complex light charged particles the calculated components well populate the high energy part of spectra. Prompt emission can therefore explain the large transverse energies experimentally observed at mid-rapidity. Received: 27 July 2000 / Accepted: 20 November 2000     

Reduction of elastic strains in directly-bonded silicon structures

The elastically strained state of the interface in directly-bonded silicon structures has been studied by x-ray diffraction topography and IR spectrometry. The pattern of the contrast observed in the x-ray topographs and the intensity oscillations in the IR spectra indicate a periodic strain distribution caused by the long-period surface microroughness on the plates to be bonded. The local microroughness did not exceed 2 Å, and it did not noticeably affect the interface structure. Two types of the structure were subjected to a comparative analysis, (i) with a smooth interface prepared by standard direct-bonding technology, and (ii) with an interface displaying a regular relief. The strain level in type-II structures was found to be lower by more than an order of magnitude. A model is proposed to account for the observed reduction of elastic strains at the bonded sections of the interface in terms of elastic relaxation of the free surfaces in the relief voids through their deflection and displacement.     

Electrostatic problem for a thin, unclosed ellipsoidal shell and disk

The axisymmetric electrostatic problem of a thin, unclosed ellipsoidal shell and disk is solved. The capacitance coefficients are calculated for a representative set of values of the geometrical parameters of the conductors. Zh. Tekh. Fiz. 69, 1–5 (February 1999)     

HPLC analysis of polycarboxylic acids used as durable press finishing agents/ organic catalysts for cellulosic material

Cotton fabric is modified by means of polycarboxylic acids in combination with an inorganic or an organic catalyst in order to impart durable press properties. After the curing process the cellulosic specimen is washed off to remove both the portion of the polycarboxylic acid that has not reacted and the catalyst applied. The treated cellulosic fabric is saponified with a sodium hydroxide solution to extract the PCA that has reacted with the cellulosic material. Both the wash liquor and the saponification liquor are investigated by means of isocratic HPLC using Aminex HPX-87-H as stationary phase. Excellent separation of the various polycarboxylic acids that are applied as crosslinking agents or as organic catalysts is achieved. The HPLC method presented enables the identification and quantification of the polycarboxylic acids. Received: 19 January 1999 / Revised: 24 March 1999 / Accepted: 28 March 1999     

Electrically conducting ion tracks in diamond-like carbon films for field emission

Electrically conducting channels in an insulating carbon matrix were produced by 140-MeV Xe ion irradiation. The high local energy deposition of the individual ions along their pathes causes a rearrangement of the carbon atoms and leads to a transformation of the insulating, diamond-like (sp³-bonding) form of carbon into the conducting, graphitic (sp²-bonding) configuration. The conducting ion tracks are clearly seen in the current mapping performed with an atomic force microscope (AFM). These conducting tracks are of possible use in field emission applications. Received: 4 May 1999 / Accepted: 5 May 1999 / Published online: 1 July 1999     

The Ternary Lanthanoid Nickel Arsenides Tb12Ni30As21 and Dy12Ni30As21 with (La,Ce)12Rh30P21 Type Related Structure

The title compounds were synthesized from the elements by reactions at high temperature. They crystallize with a hexagonal structure which was determined from single‐crystal X‐ray data of Dy₁₂Ni₃₀As₂₁: P6₃/m, Z = 1, a = 1698.5(5) pm, c = 387.7(1) pm, R = 0.053 for 797 F values and 69 variable parameters. It belongs to a large family of hexagonal structures with a metal to metalloid ratio of 2 : 1. In these hexagonal structures an ordered distribution of occupied atomic positions around the hexagonal 6₃ axis is possible only for refinements in space groups of lower symmetry. This is discussed for the present case and the very closely related structures reported for (La, Ce)₁₂Rh₃₀P₂₁ and Nd₃Ni₇P₅.     

Die Kristallstruktur von Ga5Pd13 – eine niedersymmetrische Ordnungsvariante der kubisch dichtesten Kugelpackung

The Crystal Structure of Ga₅Pd₁₃ – a Low‐Symmetrical Ordering Variant of the Cubic Close Sphere Packing Ga₅Pd₁₃ is accessible from the elements in the presence of catalytically active amounts of iodine at 520 °C. The phase decomposes at 897 °C in a peritectoid reaction. The monoclinic crystal structure was determined from the intensities of an X‐ray powder diffractogram and refined by a Rietveld profile fit: C 2/m, Z = 2, a = 2425.99(5) pm, b = 405.060(7) pm, c = 544.37(1) pm, β = 102.690(1)°, R_p = 0.069. The new structure type is described as an ordering variant of the cubic close sphere packing. The ordering pattern and the distortions in the primary coordination of the atoms reflect the definite impact of the intermetallic bonding interactions on the differentiation of the structure.