摘要:

AbstractA vibrationally coupled intervalent charge transfer theory is proposed for the copper oxide‐superconductors. The proposed B1g‐vibrational distortion exactly interchanges the chemical environment of the neighboring copper atoms. A quadruple cell is constructed to accommodate the non‐stoichiometry and a double copper‐oxide‐conducting chain with distorted symmetry is postulated. The distorted structure, prone to switching of the copper sites by vibration, is postulated to be the superconducting precursor. The left over‐oxygen, due to oxygen deficiency, is allowed to serve as a bridge between the chains and 10 oscillate with the vibration. Symmetry of the system, before and after distortion, is used to explain the spin‐angular momentum change, needed to arrive at Cooper‐paired electron/holes. The O−and O=atoms are postulated to be the bridge for superexchange and charge flow between the Cu+1/Cu+3and Cu+1/Cu+2pairs. The same theory is used to interpret the mechanisms for the following three types of copper oxide‐superconductors: YBa2Cu3OT‐x; La2‐xSrxCuO4and the newly discovered electron superconductor Nd2‐xCexCuO4‐y. The bridge oxygen oscillation may be chosen not to come from the breathing mode but from the bending deformation mode that involves the relative motion of the Cu atoms (to the oxygen) giving rise to sm

ISSN:0009-4536    

DOI:10.1002/jccs.198900068

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractIn the continuation of a review of the classification, properties and applications of mesophases, the general features of thermodynamic data of thermotropic liquid–crystalline phase transitions are surveyed. The orientation of molecules in liquid–crystalline mesophases is discussed in relation to the electrical properties. Some applications of mesophases are outlined. After surveys of both the structural classes of lyotropic mesophases and the properties of plastic crystals in cubic phases, the thermodynamic, structural and other properties of all mesophases‐are summarily considered in relation to the present state of the knowledge in this

ISSN:0009-4536    

DOI:10.1002/jccs.198900069

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractCells of lithium / Polyacetylene containing 0.5 · 1.5 M LiClO4in propylene carbonate as supporting electrolyte are constructed. The mechanism for electrochemical redox process of polyacetylene is studied using cyclic voltammetry in the potential range from −0.8 to 0.2 volt vs. S.C.E. The electrode reactions are identified to be diffusion controlled. The difference of the peak potentials between the oxidation and reduction, ΔEp, is found to be a function of the scan time per cycle (τ sec/cycle) and is influenced by concentration of supporting electrolyte and isomeric structures of polyacetylene. However, there is a better reversible redox process of polyacetylene when the ClO4−‐ ions diffuse successfully in and out of the Polymer film, which has the cis‐form structure, in concentrated supporting electrolyte solution and having a long scan time per cycle (τ). When the scan potential is extended to a more positive region, another peak is found, which may correspond to the irreversible chemical reaction caused by over‐doping. The over‐doping process is found to be controlled by the electrical field strength, concentration of the supporting electrolyte and isomerism o

ISSN:0009-4536    

DOI:10.1002/jccs.198900070

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA system for the determination of polycyclic aromatic hydrocarbons(PAHs) and chlorinated compounds in air by means of adsorption/thermal desorption(ATD) with small bed volume (0.1 g) Tenax cartridges, followed by cryogenic trap in a U‐shaped stainless steel tube with liquid nitrogen as an appropriate concentration method prior to capillary gas chromatography is described. Recoveries were determined for the complete ATD method. Desorption recoveries near 100% were found for a variety of chlorinated compounds and polycyclic aromatic hydrocarbon

ISSN:0009-4536    

DOI:10.1002/jccs.198900071

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractSimutaneous analysis of seven commonly used herbicides, 2,4‐D methyl ester, 2,4‐D methyl ester, 2,4,5‐T methyl ester, silvex methyl ester, ramrod, CIPC and DEF, by gas‐liquid chromatography with an electron capture detector was attempted. Two packed columns (which are generally used for the analysis of chlorinated pesticides) and two chemically bonded fused silica capillary columns were used for the analysis. When the packed columns were used, ramrod always interfered with the analysis of 2,4‐D methyl ester and/or silvex methyl ester. Complete separation with reasonable analysis time can be achieved using one of the chemically bonded fused silica capillar

ISSN:0009-4536    

DOI:10.1002/jccs.198900072

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractMono‐ and bi‐nuclear iron(III) complexes of general formula [FeXL] and [LFe‐Y‐FeL](Bph4)2have been prepared, and their spin state of iron atom in the complexes has been studied by means of the temperature dependence of the Mössbauer spectra, electronic spectra and magnetic measurement, where X is a mono‐ dentate ligand such as Cl‐, NCS‐, NCO‐, N3‐, pyridine and L denotes a quinquedentate Schiff base derived from salicylaldehyde and diethylenetriamine, and Y denotes bridged ligand such as pyrazine(pyr), 4,4′‐bipyridine(bpy) and 4,4′‐vinylenebipyridine(vibpy). On the basis of the Mössbauer and magnetic data, it was concluded that these complexes were all the high‐spin (S = 5/2) slate. The effect of gamma ray irradiation for these

ISSN:0009-4536    

DOI:10.1002/jccs.198900073

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractInteractions of oxygen with silver powders have been studied with a combination of angle‐resolved ESCA and volumetric adsorption. Three states of adsorbed oxygen, i.e., atomically adsorbed oxygen, dissolved oxygen, and surface oxide, are characterized by 0(1s)‐ESCA peaks at binding energies of 530.2, 532.0, and 529.3 eV respectivcly. The ESCA studies also suggest that atomically adsorbed oxygen dissolves into the subsurface of silver powders at temperatures above 100 °C, and then transforms into oxide (Ag2O) at 175 °C. Adsorbed oxygen on the silver powders was partially desorbed at temperatures higher than 180 °C. The transformation and desorption information obtained from ESCA satisfactorily explains the variation of the adsorption isotherm with temperature obtained from the volumetric adsorption of oxygen on Ag/SiO2cat

ISSN:0009-4536    

DOI:10.1002/jccs.198900074

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractStudies on the structural changes and catalytic behavior of iron‐manganese catalysts for CO hydrogenation were conducted using Mossbauer spectroscopy, X‐ray diffraction, temperature programmed reduction and kinetic measurements. It was observed that the reduction of the mixed oxide catalyst precursors proceeds via the formation of Fe3‐xMnxO4,Mn3‐xFexO4mixed spinel and Fe1‐zMn2O mixed oxide to α‐iron and MnO. After use for CO hydrogenation, catalysts are oxidized as well as carburized. The Mn3‐yFeyO4mixed spinel and Fe1‐2MnzO mixed oxide are the most powerful phases for olefin production. The highest attainable 2–4 low carbon olefin selectivity is 41% with an 86% conversion level. Higher manganese content or lower reduction temperatures may change the carbide formed from χ‐Fe5C2to the more unstable ϵ′‐Fe22C. Carbide formation is greatly dependent on manganese content and

ISSN:0009-4536    

DOI:10.1002/jccs.198900075

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe s‐p separation model INDO‐MO method has been introduced and developed for open and closed shell problems1–3In order to demonstrate the importance of σ–π interaction between 2pπ of carbon and 1s of hydrogen in this newly modified MO1we apply “McConnell Relation”4–7to a linear correlation calculation 122 data points of1H hyperfine coupling constant in the cases of free radicals and ions with π type SOMO (singly occupied molecular orbital). The calculated McConnell constant, Q, is equal to −24.6 gauss. The standard deviation and correlation coefficient of this statistical treatment are 1.011 gauss and 0.980, respectively. Most of the results in this calcula

ISSN:0009-4536    

DOI:10.1002/jccs.198900076

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe photodissociation of methyl iodide in various matrices at low temperature was studied. The observed Raman spectra excited by 514.5 nm laser radiation showed that there were two different photolytically produced iodine species isolated in the matrices after illumination by a medium pressure mercury lamp. One species which was dominant at lower iodine concentrations and exhibited a progression with an ωe of 201 cm−1, belonged to the matrix isolated iodine monomer (I2). The other species, which was dominant at higher iodine concentrations with an ωeof approximately 180 cm−1, belonged to the iodine aggregate ((I2)n). Five progressions of resonance Raman or resonance fluorescence of these two species were also observed in the other matrices. The iodine aggregate in the methyl iodide matrix at 77 K was formed in a crystalline structure, while the photolytically generated iodine aggregate from CH3I/Ar (2/3) matrix at 10 K, after illumination with a mercury lamp, was in amorphous form. The rearrangement of photolytically produced iodine aggregate in methyl iodide matrix was observed as a function of the duration of illumination. Local heating effects of the laser radiation might induce the iodine monomer to aggregate in matrices. The photodissociation mechanism of methyl iodide in matrices is also pro

ISSN:0009-4536    

DOI:10.1002/jccs.198900077

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY