摘要:

AbstractThe luminescence properties of Bi2MoO6, Bi2MO2O9, and Bi2(MoO4)3are reported. Excitation bands peak in the violet, and emission bands in the red spectral region. The results are discussed in connection with the crystal structures and compared with those of the corresponding tungstates. The luminescence of γ'‐Bi2MoO6suggests fourfold coordination for molybdenum in the pha

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881002

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

年代:1984

数据来源: WILEY

摘要:

AbstractBy activation of the new host lattice Ca2La0.5Na0.5WO6with trivalent rare earth ions an emission in the visible (Ln3+= Sm, Eu, Dy, Ho, Er, Tm) or near infrared region (Nd, Ho, Er, Tm, Yb) is observed. Energy transfer from Nd3+to Yb3+and Er3+, Tm3+, Yb3+to Ho3+has been found to occur. The excitation, emission and diffuse reflectance spectra are discussed and compared to the properties of the systems Sr2La0.5Na0.5WO6: Ln3+.

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881003

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe degradation of a polyacetylene (PA) anode as proposed in PAy+(ClO 4−)y/LiClO4/PC type half cells has been investigated by resonant Raman scattering. – During electrochemical cycling, which modelled the operation of a PA/Li cell as a rechargeable storage battery, degradation becomes evident after only a few cycles. The charge regainable in the reduction steps after the seventh step is only 80 percent of the charge transferred in the preceding oxidation step. – The resonance Raman spectra have been analysed according to the method of Kuzmany which yields informations on the length distribution of conjugated segments in the sample. At the beginning of cycling a distribution of long segments and a distribution peaked at segment lengths around 5 double bonds have been found to coexist. After 7 cycles the long segments are already affected by the degradation and after a total of 27 cycles the Raman spectrum reveals the complete absence of conjugated segments longer than 10 doubl

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881004

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe temperature dependences of1H NMR spin‐lattice relaxation times and1H NMR second moments were observed for guanidinium chloride, bromide, iodide, thiocyanate, nitrate, and perchlorate. The results of the NMR experiments carried out with the crystals of these compounds except the last one can be interpreted in terms of the C3reorientation of the cation about its symmetry axis. The solid‐solid phase transition at 454 K reported for guanidinium perchlorate could be resolved into two phase transitions taking place successively at 450 and 452 K. In the low temperature phase of this salt, the C3reorientation of the cation is activated. The occurrence of cationic self‐diffusion in the high temperature phase was confirmed by the measurements of1H NMR relaxation times. The NMR motional parameters are evaluated for these cationic motions in the present salts. The phase transition temperature of guanidinium iodide was strongly depended on the grain size of the sample employed. Guanidinium bromide yielded a single81Br NQR line at room temperature indicating that all bromide ions in the crystal are crystallographically equivalent in agreement with the results of X‐ray a

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881005

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

年代:1984

数据来源: WILEY

摘要:

AbstractZero field splitting (ZFS) parameters for [MnCl6]4‐in three Cd compounds were determined and the validity of the superposition model was demonstrated by the consistent values of the intrinsic ZFS parameter b̄2 in all three cases as well as by a detailed comparison of the experimental ZFS pattern for one compound with that calculated from the crystal structure data. Additional ZFS data for [MnCl6]4‐from the literature are also shown to lead to only slightly variable values ofb̄2. – The change of the intrinsic ZFS parameterb̄2from a negative value for F−to a larger positive value for Cl−as ligand is shown by detailed calculations for the various mechanisms to be due to the superponable overlap and covalency contributions as a result of increased charge transfer and ligand spin‐orbit coupling constant. The reliability of such calculations is still limited by the lack of experimental data for the transferred

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881006

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe magnetic susceptibility of liquid Rb – Au alloys and the optical absorption of the solid and liquid equimolar alloy RbAu have been measured up to temperatures of 1000°C. The optical gap of solid RbAu shows Urbach type behaviour withE0= 2.75 ± 0.1 eV. On melting it is reduced by about 1 eV:Eg(510°C) = 1.35 ± 0.1 eV. The magnetic susceptibility exhibits a strong diamagnetic minimum near the equiatomic composition yielding further evidence that liquid RbAu is semiconducting and predominantly ionic in bonding. The observed deviation from the expected susceptibility value for purely ionic RbAu and the high optical absorption in the near infrared suggest that localized paramagnetic electron states exist in the ionic liquid, possibly in equilibrium with free carriers. Like Cs – Au the alkali metal‐gold system Rb – Au thus closely resembles the alkali metal‐halogen systems the major differences arising from the reduced charge transfer and chemical ordering in

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881007

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

年代:1984

数据来源: WILEY

摘要:

AbstractBy79,81Br−and127I NQR the hydrobromides of glycine, l‐alanine, l‐leucine, l‐proline, semicarbazide and the hydroiodides of l‐leucine and semicarbazide were studied in the temperature range 77 ≦T/K

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881008

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

年代:1984

数据来源: WILEY

摘要:

AbstractElectron transfer reactions occurring at n‐GaP (111) and (100) electrodes have been investigated in acetonitrile solutions. In the presence of strongly oxidising cations, such as 10‐methylphenothiazine (10‐MP+·), Ferrocene (Cp2Fe+) and tetrathiafulvalen (TTF+·), it is shown that electron transfer proceeds directly from the conduction band to cations adsorbed at the semiconductor surface. Differential capacitance and photo/dark‐current measurements have been used to identify a considerable positive shift of the flatband potential (UFB) in the presence of the oxidising cation. This phenomenon is absent in the presence of a similarly oxidising neutral species. No evidence was obtained to support the model which proposes mediated electron transfer via surface states deep in the

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881009

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

年代:1984

数据来源: WILEY

摘要:

AbstractExtremely small CdS particles were prepared in propanol−2 solution at − 78°C and in aqueous solution in the presence of sodium hexametaphosphate at room temperature. These colloids are colorless. Their UV absorption spectra exhibit several maxima. Aging of the colloids is accompanied by intensity variations in the absorption maxima and by a shift of the onset of absorption to longer wavelengths. These small CdS particles hardly possess semiconductor properties (Q‐state CdS). A semi‐classical treatment of the energies of an electron‐hole pair in these particles yielded the wavelengths of their absorption spectra. At the small particle sizes used, the first excited state was reached by photon‐absorption in the UV, and the second excited state was generally not reached at all. The various maxima in the absorption spectra are explained in terms of a size distribution of the colloids with preferential agglomeration numbers. Reasons for the formation of such a structured size distribution are given. The fluorescence and fluorescence excitation spectra of the small particles were also investigated. Particles below a certain size have only one broad fluorescence band at a much longer wavelengths than the onset of absorption. As the particle size increases, this band is shifted towards longer wavelengths, and finally an additional rather sharp band appears at the threshold of absorption. CdS colloids in the Q‐state can be made which fluoresce as desired anywhere between the red and the blue. Also reported are the first experiments in which the preparation of Q‐type CdS in the solid state is achieved by evaporating the solvent from the col

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881010

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

年代:1984

数据来源: WILEY

摘要:

AbstractNeutron diffraction experiments on liquid formic acid of the five isotopically different forms DCOOD, DCOOH, HCOOD, 0.36 DCOOD + 0.64 DCOOH, and 0.36 DCOOD + 0.64 HCOOD were performed. Inelastic scattering corrections had to be performed in a particularly careful way considering that H is a strongly incoherent scatterer. From the five corrected coherent cross sections and the corresponding weighted sums of pair correlation functions a first set of intramolecular structure data is derived. A suitable decomposition of the primary experimental material in selected groups of pair correlation functions served to work out further structural details which showed that formic acid in the liquid state is a molecule for which the OH group is rotated by about 50° out of the molecular plane

ISSN:0005-9021    

DOI:10.1002/bbpc.19840881011

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

年代:1984

数据来源: WILEY