摘要:

AbstractStarting from the solution of the potential equation in bipolar coordinates the forces and torques acting on the cylinders are calculated. In contrast to two earlier papers, a periodic field and dissipative media are anticipated. Cylinders of different radii and material are assumed in general. Whereas the forces on the cylinders are equal in magnitude but of opposite sign, the torques are in general different. If only one of the cylinders has a vanishing loss angle a “uni‐lateral” torque exists. In the case of identical cylinders the expressions for the interactions are essentially simplified, the torques being identical in magnitude and sign. – There is little hope to obtain closed solutions of the analogous problem in 3 dimensions (spheres, ellipsoides, etc.) that is of high practical interest. However, the information gained from the most simple “two dimensional” example allows for a valuable qualitative gen

ISSN:0005-9021    

DOI:10.1002/bbpc.198800351

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractThe frequency dependence of forces and torques acting on two parallel cylinders in a periodic field is investigated. The permittivities are assumed to have imaginary parts a) due to an electric conductance or b) due to a single Debye relaxation. At the transition frequencies a change of the sign of the force components or of the torque can take place. Marked deviations from the “long distance laws” occur for small cylinder distan

ISSN:0005-9021    

DOI:10.1002/bbpc.198800352

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractThe interactions between two dielectric bodies in an outer field show rather strong deviations from the “long distance laws” if the surfaces of the two bodies approach contact. Image forces occur that require another type of mathematical procedure. Instead of a partial differential equation an integral equation has to be solved. In the special case of cylindrical bodies these solutions lead to Fourier transforms that can be integrated explicitly (in contrast to the case of two spheres where the integral equation is not yet solv

ISSN:0005-9021    

DOI:10.1002/bbpc.198800353

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractThe experimental arrangement of a time‐of‐flight mass spectrometer with multi‐photon ionization and electron impact ionization is described. This set up was combined with a discharge flow reactor and a molecular beam sampling device. The detection of the radicals CH3, C3H5, CH2OH and their deuterated analogs by the wave‐length selective multi‐photon ionization allowed the identification of primary products of elementary reactions in the gas‐phase (around 1 mbar). The branching ratios for the reactions\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm O} + {\rm C}_2 {\rm H}_4 \to {\rm CH}_3 + {\rm HCO}} \\ {{\rm F} + {\rm C}_2 {\rm H}_6 \to {\rm CH}_3 + {\rm C}_2 {\rm H}_3 {\rm F}} \\ {{\rm F} + {\rm c - C}_{\rm 3} {\rm H}_6 \to {\rm c - C}_{\rm 3} {\rm H}_{\rm 5} + {\rm HF}} \\\end{array} $$\end{document}were determined as (0.5 ± 0.15), (0.5 ± 0.1), (0.95 ± 0.05), respectively. – For the reactions of the CH2OH and CH3O radicals with H and O atoms, the following reaction paths were established:\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l}{\rm CH}_2 {\rm OH/CH}_3 {\rm O} + {\rm H} \to {\rm CH}_3 + {\rm OH }\,\left({30\%} \right) \\ {\rm CH}_{\rm 2} {\rm OH} + {\rm D} \to {\rm CHDOH} + {\rm H} \\ {\rm CH}_{\rm 3} {\rm O} + {\rm O} \to {\rm CH}_{\rm 3} + {\rm O}_{\rm 2} \left({ > 50\%} \right). \\\end{array}

ISSN:0005-9021    

DOI:10.1002/bbpc.198800354

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractBenzophenone – isopropyl alcohol – acetonitrile, benzophenone – benzhydrol – acetonitrile and acetone – isopropyl alcohol – acetonitrile systems were studied by laser flash photolysis transient absorption technique and by steady‐state quantum yield determinations. Kinetic parameters were derived for reactions of the ketyl radicals formed in the primary photoreduction steps. The room temperature overall rate coefficients at 0.001 mol dm−3benzophenone and 2.6 mol dm−3isopropyl alcohol in acetonitrile are in 108dm3mol−1s−1units: 12.8 ± 0.6, 8.0 ± 0.4 and 0.59 ± 0.01 for Mc2ĊOH + Me2ĊOH, Me2ĊOH + Ph2ĊOH and Ph2ĊOH + Ph2ĊOH, respectively. (The error limits represent 2 standard deviations.) Combination was shown to be the only significant reaction in the interaction of two Ph2ĊOH radicals, while disproportionation is the dominating path in the reactions inolving Me2ĊOH radicals. Evidences are presented for the existence of four reaction channels in the cross reaction of the two ketyl radicals. These are combination (4a), disproportionations (4b) and (4c) and formation of a “light absorbing transient” (4d), with branching ratiosk4a/k4= 0.18 ± 0.08,k4b/k4= 0.61 ± 0.11,k4c/k4= 0.05 ± 0.02 andk4d/k4= 0.18 ± 0.03, respectively. – The radical transfer reaction Me2ĊOH + Ph2CO → Me2CO + Ph2ĊOH, which may change considerably the product distribution and quantum yields in the photoreduction of benzophenone by isopropyl alcohol at medium and low light intensities, was investigated by quantum yield determinations and a room temperature rate coefficient ofk5= (7.3 ± 1.2) · 104dm3mol−1s−1was extracted through computer model simulation. This rate coefficient is co

ISSN:0005-9021    

DOI:10.1002/bbpc.198800355

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photochemistry of the following azide complexes in organic solvents has been investigated: [Au(N3)4]−, [Au(N3)2]−, [Ag(PPh3)2N3], [Pt(N3)6]2, [Pt(N3)4]2−, [Pd(N3)4]2−, and [Pd2(N3)6]2−. All complexes underwent a photochemical reduction of the metal and oxidation of azide upon ligand to metal charge transfer excitation. The photolysis of the complexes with the metals in the lower oxidation states (Au(I), Ag(I), Pt(II), Pd(II)) led ultimately to the generation of free metals which form colloids. These colloids were characterized by their absorption spectra which showed the typical plasmon bands in the case of gold and silver. Pt(0) and Pd(0) produced during the photolysis can be intercepted with allyl chloride to form [Pt(π‐allyl)Cl]4and [Pd(π‐allyl)Cl]2. Most photoreactions took place with rather large

ISSN:0005-9021    

DOI:10.1002/bbpc.198800356

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractTriplet‐singlet annihilation (TSA) T, +1Δg→ S1+3Σg−of the metastable triplet state (T1) of an aromatic compound and the metastable singlet state (1Δg) of molecular oxygen may lead to an observable delayed fluorescence (DF) S1→ S0(DF of the Kautsky‐Müller type). A DF of this type has been observed with liquid solutions of phenanthrene and quinoxaline in perfluorohexane and of fluoranthene in 1,1,2‐trichloro‐1,2,2‐trifluoroethane in the presence of oxygen. The DF due to TSA can be kinetically distinguished from the DF due to triplet‐triplet annihilation (TTA). The results indicate a very long lifetime of1Δgin perhalogenated alkanes. The DF from phenanthrene due to TTA can be assigned to the fluorescence

ISSN:0005-9021    

DOI:10.1002/bbpc.198800357

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractA new type of crystals of the reaction center I complex, RC I, of water splitting photosynthesis has been prepared from the cyanobacterium Synechococcus sp. In contrast to our first crystals (11), the new ones have a length of up to 1 mm, a thickness of up to 50 μm and show X‐ray diffraction patterns with a resolution of about 4 Å. The space group of the hexagonal crystals is probably P6322. One RC I represents the asymmetric unit. The unit cell dimensions area=b= 285 Å,c= 167 Å, α = β = 90° and γ = 120°. The building block of the crystal lattice is a trimer (diameter ˜19 nm, height ˜6 nm, and apparent mass ˜600 kDa). The trimer is composed of 3 identical RC I units so that the quaternary structure is α3. The unit cell harbors four trimers in two layers with tw

ISSN:0005-9021    

DOI:10.1002/bbpc.198800358

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractUsing an exponential distribution function for the energy of the adsorption sites on a heterogeneous surface, an equation for multilayer adsorption is obtained. The basic assumptions are similar to those of the Frenkel‐Halsey‐Hill model (FHH). The equation deduced here is however somewhat different: a (θ +B)rterm appears instead of the FHH θrterm, where θ is the coverage,Bis a constant related to the parameters of the exponential distribution function, andris the exponent governing the decrease of energy with increasing distance from the surface. The addition of constantBto θ improves the linearity of the usual logarithmic plot of the equation and increases the value ofras compared with that from the FHH equation. The model is applied to the analysis of adsorption isotherms of N2at 77 K on SiO2and Sc2O3. Values obtained forrare close to 3, the theoretical exponent for the interaction due to dispersion

ISSN:0005-9021    

DOI:10.1002/bbpc.198800359

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY

摘要:

AbstractInterrelations of thermodynamic equations of state of adsorbed phases are considered. These relations are consequences of the fact that an adsorbate, assumed to be a thermodynamic system in the sense of Schottky, has a number of degrees of freedom which compared to that of a bulk phase is reduced by one. Depending on the choice of independent variables several forms of these interrelations can be formulated. Here especially relations between the adsorption isotherms of a multi‐component adsorbate, using the partial pressures and the temperature of the surrounding adsorptive as independent variables are considered. By these relations the number of independent parameters included in the isotherms is reduced considerably. This is demonstrated by discussing multi‐component adsorption isotherms of the Langmuir‐Freundlich – and of a generalized B

ISSN:0005-9021    

DOI:10.1002/bbpc.198800360

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1988

数据来源: WILEY