bluuebunny/crossref_metadata_2025_split huggingface dataset:
Single molecule spectroscopy in solids: Quantum optics and spectral dynamics
Authors: Basché Th. , Bräuchle C. 
Published: July 2012

AbstractIn recent years different microscopic and spectroscopic techniques were successfully employed to detect the fluorescence signals of single dye molecules in the condensed phase. In low temperature solids the fluorescence excitation line of a single dopant molecule is a high resolution optical probe of its local nanoenvironment. As inhomogeneous contributions and ensemble averaging are absent, many effects hidden when looking at large populations of molecules become observable. Two important research areas in single molecule spectroscopy deal with the investigation of quantum optical effects and the spectral jumping behaviour of single molecule excitation lines caused by fluctuations of two‐level systems inherent to disordered solids. Rather than delivering a complete presentation, we will focus on some selected examples which emphasize the unique features of spectroscopy with a single absorber.
Reactivity of the oxide growth process on zr metal in aqueous potassium iodide and other alkali halide solutions
Authors: Ghoneim A. A. , Ameer M. A. , Saleh H. M. , El Heakal F. ‐Taib 
Published: July 2012

AbstractThe kinetics of growth of an oxide film on Zr electrode under open circuit conditions in Kl solutions were investigated using potential and impedance measurements. The effect of some parameters such as surface pre‐treatment, concentration and salt type, including alkali halide anions, on the reactivity of the oxide growth process were studied. In all cases the potential, capacitance and resistance were followed with time, and the oxide film was found to thicken continuously.The iodide ion is assumed to participate in enhancing the formation of species which inhibits partially the growth of oxide film on Zr surface. The impedance diagrams of the oxide film/electrolyte interface is an almost capacitative one, with an impeded charge transfer reaction.
Systematic investigation of the global phase behavior of associating binary fluid mixtures: I. mixtures containing one self‐associating substance
Authors: Kraska T. 
Published: July 2012

AbstractGlobal phase diagrams have been calculated for binary mixtures containing one self‐associating and one isotropic substance. The calculations have been made on the basis of an equation of state. This equation consists of the van der Waals equation as isotropic part and the association term of the Statistical Association Fluid Theory (SAFT) equation. The results are presented in two‐dimensional intersections of the global phase diagram. The influence of the self‐association on the binary behavior is discussed. Comparisons with similar investigations of the van der Waals, Redlich‐Kwong, and Carnahan‐Starling‐Redlich‐Kwong equations of state have been made. Further comparisons with recent calculations of binary water systems have been accomplished.
I. Glass Transition. Theoretical concepts on the glass transition of polymers and their test by computer simulation
Authors: Binder K. 
Published: July 2012

AbstractVarious organic molecules, in particular polymers, are extremely good glass formers and allow the study of supercooled melts near the glass transition in metastable equilibrium. Theories of the glass transition imply such an equilibrium (e.g. mode‐coupling theory, or Gibbs‐di Marzio theory) and can hence be tested in these systems.Simplified lattice models for polymer melts (e.g. the bond fluctuation model) have been developed that can very efficiently be studied by Monte‐Carlo simulation, and although they fail to accurately describe the local structure, they describe many features of the experiments very well. In this model, the mechanism of the glass transition is a competition between the (energetically favorable) local stretching of effective bonds, and the (entropically favorable) dense packing of effective monomers (“geometric frustration”). It is shown that the model exhibits a dramatic slowing down upon cooling, and the properties of the frozen‐in glass distinctly depend on the cooling rate. While the Gibbs‐di Marzio theory predicts correctly the temperature region where the configurational entropy of the supercooled melt strongly decreases, the vanishing of the entropy is traced back to a severe underestimation of the entropy of the reference state (high temperature melt). The idealized version of the mode‐coupling theory (involving critical singularities above the freezing transition) is found to be not very useful either, as the singularities are strongly rounded. But the extended version of the mode‐coupling theory which describes this rounding, is in nice agreement with the simulations.
Progressive transformation from quartz to amorphous silica by shock pressure: Role of theα→βtransition
Authors: Chemarin C. , Panczer G. , Badjukov D. D. , Champagnon B. 
Published: July 2012

AbstractThe transformation from crystallineα‐quartz to silica glass under shock pressure is followed, in the intermediate phase where both crystalline and amorphous SiO2are detected, by Raman microspectrometry. Experiments are carried out on samples recovered from increasing peak pressure. The evolution of the crystalline phase is compared to the evolution ofα‐quartz with a thermal annealing. No observation is made for aβ‐phase transformation before full amorphization of the material.
Phosphorescent glass
Authors: Bauerecker S. , Roch Th. , Cammenga H. K. 
Published: July 2012

AbstractUsing low‐melting enamel glasses it could be managed to develop a protecting glassy embedding for luminescent pigments. Such a lasting protection from greying ‐ especially against UV light in the presence of humidity ‐ offers new operational areas to luminescent pigments like the outdoor area. In the present work the luminescence spectra and decay functions of phosphorescent glasses are examined. For a ZnS pigment and a newly developed SrO‐aluminate pigment of high phosphorescence efficiency it could be shown that the emission spectra of the phosphorescent glasses do not essentially differ from those of the pure pigments. The phosphorescence efficiency of ZnS phosphorescent glass could be increased by more than 10 per cent by reducing the TiO2 content regarded as optimal up to now. First experiments show that an SrO‐aluminate pigment can also be embedded in a glassy matrix. Indeed, intensity losses of 70 per cent appeared. Here a high potential of improvement is to be assumed. Further investigations are necessary. In addition we have found that the phosphorescence decay functions of the samples under investigation depend on the excitation time. The phosphorescent glass can be universally applied as granules or as formed bodies and offers manifold applications.
II. Crystallization. Crystallization of glass forming melts
Authors: Gutzow I. , Dobreva A. 
Published: July 2012

AbstractA survey on the kinetics of nucleation and the mechanisms of crystal growth is given. Theoretical and experimental developments verifying the more general, non steady state formulation of the theory of nucleation are discussed. It is argued that the experimentally observed transiency in the kinetics of nucleation in glass forming systems may be due to both non steady state time lag as well as to growth effects. In order to distinguish between both cases, an analysis of the temperature dependence of the induction times, t, and a comparison with the temperature dependence of the non steady state time lag and the rates of nucleation and growth are required. Experimental results on the mechanisms of crystal growth are provided.
Direct spectroscopic investigation of phase formation in glasses containing semiconductor microcrystals in correlation to their luminescence properties
Authors: Müller M. , Woggon U. 
Published: July 2012

AbstractThe formation of CdSe microcrystals in a glass matrix is studied by UV‐Vis in situ spectroscopy. Hereby the temperature range is found where nucleation takes place. The size distribution of the CdSe microcrystals depend on the growth rate, this means on growth temperature. The electronic properties which depend on the size of the CdSe quantum dots are investigated by photoluminescence and pump‐probe‐spectroscopy. The luminescence spectra give hints that more than one ‘family’ of CdSe microcrystals was grown during heat treatment.
Precipitation of hollandite whiskers within a tielite matrix via the sol‐gel process
Authors: Kohn Sandro , Jansen Martin 
Published: July 2012

AbstractIn the system K‐A1‐Ti‐O the precipitation of a aluminium titanate ceramic, penetrated by potassiumhollandite whiskers, was established via the sol‐gel process. The crystallization by internal precipitation of the two phases tielite Al2TiO5 and potasiumhollandite K2Al2Ti6O16 from the amorphous sol‐gel powder was examined by X‐ray powder diffractometry, 27Al‐MAS‐NMR, DTA/TG and SEM/EDX. It has been shown, that the hollandite phase crystallizes in the shape of a whisker beside the tielite matrix. Such hollandite crystals have potential as new ceramic whiskers for the purpose of the reinforcing ceramics. Thus a texture of high density, penetrated by whishers, is obtained.
AIPO4‐containing glass‐crystalline materials in the system Li2O‐Al2O3‐P2O5
Authors: Jęczmionek L. , Kucharski J. , Wasylak J. 
Published: July 2012

AbstractPublication concerns the crystallization of glasses in the system Li2O‐Al2O3‐P2O5. The aim of this study was to determine the area of the occurrence of glasses in the system Li2O‐Al2O3‐P2O5 to examine their tendency for crystallization of AlPO4 phase and others in the process of thermal treatment. Applying the method X‐ray diffraction the crystallization mechanism of AlPO4 (cristobalite and tridymite form) and other accompanying phases, and the influence of the addition of small amount of SiO2 on the crystallization of these glasses was examined. The structure of glasses and glass‐crystalline materials obtained were defined by means of infrared spectra. AlPO4 glass‐crystalline materials have satisfying resistant properties to use them as coats on steel.
Directed crystallization of glasses in the system SiO2‐CaO‐MgO+(ZnO+Li2O) nucleated with MoO3 and WO3
Authors: Wasylak J. , Kucharski J. 
Published: July 2012

AbstractIn the glass‐crystalline materials obtained through the directed nucleation, the main principal is to determine the optimum quantity of nucleating catalyst needed to bring about fine‐crystalline phase in the glass during heating. The methods of choosing the catalyst are very well known, but sometimes some of them are labour‐consuming and complicated equipment are demanded.In this work a simple and quick method of choosing the catalyst to produce glass‐crystalline materials was examined. The method is elaborated on the DTA analysis curves basis. Investigations were made on the system SiO2‐CaO‐MgO+(ZnO+Li2O) nucleated with molybdenum and tungsten oxides.Influence of different amounts of catalyst on crystallization process of different particle size glass samples was determined using characteristic points on DTA curve.
Compositional influence on shape and position of the first sharp diffraction peak (FSDP) in silicate and germanate glasses
Authors: Göttlicher J. , Pentinghaus H. J. 
Published: July 2012

AbstractSilicate and germanate glasses studied by X‐Ray diffraction methods (WAXS) show characteristic features concerning the first peak of their scattering functions (FSDP: first sharp diffraction peak). Shapes and positions of the FSDPs develop systematically with composition. The shape of the FSDPs can only be described by introducing up to three peaks. We assume that the glass networks are heterogeneous in the scale of medium range order with respect to their chemistry and/or topology and these regions are mainly connected coherently.
Preparation and spectroscopy of lead‐tin fluorophosphate glass doped with TPPS and TPPS‐Sn
Authors: Orihara Yuichi , Uo Motohiro , Inoue Hiroyuki , Makishima Akio , Tani Toshio 
Published: July 2012

AbstractTetraphenyl‐porphine‐tetrasulfonic acid (TPPS), which is a well known dye for photochemical hole burning (PHB), and its Sn complex (TPPS‐Sn) were incorporated into a low melting SnF2‐P2O5‐SnO‐PbF2 glass system with a conventional melting method. From the absorption and luminescence spectroscopy, it was found that in the glass the above organic dyes were not decomposed and the original structure of TPPS‐Sn was maintained, however the structure of TPPS changed from that in the aqueous solutions. The excitation spectra and the extraction of the dyes suggest that TPPS reacted with Sn during melting, and TPPS‐Sn. TPPS and/or TPPS‐Sn with one pyrrole reduced were produced. This is supported by the result of PHB measurement.
Formation of amorphous and nano‐crystalline carbon in C+ implanted silica glass
Authors: Herrmann U. , Wendler E. , Dunken H. H. , Wesch W. , Seifert F. 
Published: July 2012

AbstractRutherford backscattering spectrometry, VIS‐NIR transmission of IR reflection measurements as well as Raman investigations have been used to characterize C+ implanted (30 keV, 0.5×1016cm‐2) silica glass. Distribution of implanted ions can be described by a Gaussian profile with a maximum at about 80 nm. C+ ions penetrate to a depth of 180 nm in the substrate material. Transmission spectra in the VIS‐NIR region were simulated with the dielectric functions of substrate glass and amorphous carbon using a multilayer model. Evaluation of the IR reflectance spectra indicates the creation of CO and a damage of the glass structure up to a depth of about 300 nm. Raman measurements of implanted samples show the aggregation of amorphous carbon. Anneling of samples for one hour at 700 or 1000°C in nitrogen atmosphere leads to the formation of nano‐crystalline carbon precipitates. Furthermore, the relaxation of the glass structure and the existence of Si‐C bonds has been observed after heat treatment.
Photoluminescence of a soda lime glass exchanged with silver ions
Authors: Villegas M. A. , Paje S. E. , Llopis J. , Fern Navarro J. M. Ández 
Published: July 2012

AbstractA commercial soda‐lime glass subjected to ion exchange with Ag+ at different temperatures and times is studied by photoluminescence (PL), optical absorption (OA) and transmission electron microscopy (TEM). Some samples were reheated in air and in a reducing atmosphere (N2 ‐ H2) to favour the reduction of the Ag+ ions. The evolution of the silver colloids with the exchange parameters is monitored by means of the caracteristic absorption band at 420 nm.PL spectra reveal that the samples exchanged with silver show a broad emission band centered around 600 nm upon excitation in the nearby ultraviolet, which intensity is very sensitive to temperature and exchange time. The excitation spectra exhibit a broad band with three peaks at about 360, 395 and 445 nm related to different types of silver centres.
On the incorporation of copper ions in heavy metal fluoride glasses
Authors: Scholz G. , Stößer R. , Sebastian S. , Grande T. , Aasland S. , Nofz M. 
Published: July 2012

AbstractCu2+ ions incorporated into (ZBLAN) fluoride glasses reflect via distributions of spin coupling parameters local randomness of the glass matrix. Cw‐X‐band ESR measurements at 4.2 K applying different values of the microwave power as well as computer simulations have shown that even at very low copper concentrations (<0.6 mol%) the Cu2+ ions form point defects coexisting and weakly interacting with magnetically coupled species. The tendency of Cu2+ ions to form aggregates is remarkedly higher than in oxide glasses which corresponds to a nonuniform distribution of the paramagnetic centres in the glass matrix. After cyclic heating and cooling processes, recrystallization of the matrix represented by lowering the line widths, and resolving hyperfine splittings in the g∥ region could be observed.
Relationships between glass structure and spectroscopic properties of Eu3+ and Tb3+ doped glasses
Authors: Ebendorff‐Heidepriem H. , Ehrt D. 
Published: July 2012

AbstractFluoride phosphate and phosphate glasses were doped with Eu3+ and Tb3+ ions. The relationships between glass structure and spectroscopic properties of the doped ions were of interest to obtain information about the local glass structure around rare earth ions.Nephelauxetic shift of Tb3+ f→d absorption band, Eu3+ fluorescence intensity ratio of 5D0→7F2 to 5D0→7F1 as well as electron‐phonon coupling strength and phonon energy determined from Eu3+ phonon sideband spectroscopy were studied in dependence on phosphate content of the host glasses. Tb3+ fluorescence intensity ratio of 5D4→7FJ to 5D3→7FJ (J= 0,1,2… 6) transitions is affected by Tb3+ concentration and OH content of the glasses.With increasing phosphate content of the glasses, the covalency between rare earth ions and surrounding ligands increases due to substitution of fluoride ions by oxygen ions having higher electron polarizability. This effect leads to increasing nephelauxetic shift, Ω2 parameter and electron‐phonon coupling strength. In fluoride phosphate glasses, the diphosphate groups dominate the spectroscopic properties of the rare earth ions. The Tb3+ fluorescence intensity ratio of 5D4→7FJ to 5D3→7FJ increases with increasing Tb3+ concentration and OH content, respectively, due to acceleration of cross‐relaxation between Tb3+ ions and due to energy transfer from Tb3+ ions to OH groups.
Structure and cation sensitivity of silicate glasses ‐ a review
Authors: Thomas B. , Scholz K. , Herzog K. 
Published: July 2012

AbstractSilicate glasses of different compositions can be used as materials for ion sensitive electrodes. We have investigated glasses of the systems Na2O‐SiO2, Na2O‐RO‐SiO2 (R = Ba, Sr, Ca, Mg, Be, Cd, Zn), and Na2O‐R2O3‐SiO2 (R = Ga, Al, B) in a wide composition range to find relationships between the electrochemical properties (electrode sensitivities and selectivities) and the microstructures of the compact glasses and their hydrated layers. Various NMR spectroscopic techniques have been used (MAS, CP‐MAS, CRAMPS, SATRAS, REDOR) for probing the glass structure. Principal Component Analysis was found to be useful to test possible correlations between the composition, the glass structure parameters and electrode properties.
Electroluminescence with organic compounds
Authors: Salbeck Josef 
Published: July 2012

AbstractSome fundamental aspects of basic principles and applications of electroluminescence, based on organic low molecular weight compounds and polymeric compounds will be presented. The basic working principles and the basic construction of electroluminescent devices are described. Some factors affecting the efficiencies and lifetime or organic electroluminescent devices are reviewed, describing recent developments in dye‐based organic hetero‐junction and polymer systems. The distinctive advantages of these organic LEDs are high efficiency of all colors and potential ease of fabrication, offering the possibility of applications in flat‐panel displays. No attempt is made in the present article to review the whole field, but instead this interesting field is described by focusing on a few selected topics, and by describing few representative results.
Thermal contributions in infrared laser induced grating experiments at high pressure
Authors: Dreizler A. , Latzel H. , Dreier T. , Koch A. , Wolfrum J. 
Published: July 2012

AbstractDegenerate four wave mixing (DFWM) and laser induced thermal grating spectroscopy (LITGS) have been used to detect ethylene and methanol in mixtures with nitrogen, argon or helium in the pressure range between 0.005 and 18 bar. The grating forming step for both techniques was accomplished via absorption of radiation in the interference region from two beams from a single longitudinal mode CO2 laser. For DFWM the same CO2 laser and for LITGS a diode pumped Nd: YAG laser were employed to read out the transient grating. Using photo thermal deflection spectroscopy (PDS) as an independent spectroscopic method thermal effects were confirmed for total pressures above 0.1 bar. For both DFWM and LITGS signal intensities increased with buffer gas pressure due to collision induced transfer of optical excitation energy into translational degrees of freedom. The temporal behaviour of the IR‐grating generation and thermalization processes and the advantages of hydrocarbon trace species detection from thermal gratings at high pressures is discussed.
A differential anomalous X‐ray scattering study of lead(II)acetate trihydrate in 2‐methoxyethanol
Authors: Beudert R. , Batschkowitsch S. , Bertagnolli H. , Gutwerk D. , Kolb U. , Weigelt J. 
Published: July 2012

AbstractThe results of a differential anomalous X‐ray scattering (DAS) study on lead(II)acetate trihydrate, dissolved in 2‐methoxyethanol, are reported. Anomalous X‐ray scattering at two energies below the L3‐edge of lead (Pb) was used to determine the local environment of Pb and to get more precise information on the complex molecular structure of the liquid. The differential scattering intensities and their Fourier transform, the differential atom pair correlation function (DACPF), were obtained after an intricate data evolution procedure. The analysis of the DACPF provides strong evidence for a dimeric structure of lead(II)acetate trihydrate in the methoxyethanolic solution via lead ‐ oxygen ‐ lead correlation.
Photoelectrochemical investigations of complex formation phenomena on oriented n‐pyrite (FeS2) crystal surfaces
Authors: Büker K. , Alonso‐Vante N. , Tributsch H. 
Published: July 2012

AbstractQuantum yields of illuminated single crystalline n‐pyrite (FeS2)/electrolyte junctions were measured at λ = 632.8 nm and found to be significantly higher in the presence of negatively charged redox species, such as I− and [Fe(CN)6]4− in contrast to species like Fe2+. Higher photocurrents and photovoltages at (100) n‐pyrite rotating disc electrodes in comparison with (111) electrodes fabricated from the same single crystal are obtained. Further, (100) n‐pyrite electrode surfaces were treated with pyrazine and 4,4'‐bipyridine. A significant decrease of dark current and a shift of the equilibrium potential in 0.5 M FeSO4 is ascribed to chemical complex formation between the electron donating ligands and the Lewis acidic Fe(II) centres of the (100) n‐pyrite surface. In the case of pyrazine treatment an enhancement of photocurrent and photovoltage could be observed. The observed phenomena are discussed in terms of coordinated chemical surface complex formation and charge transfer properties.
Pressure effect on the ene reaction of singlet oxygen with tetramethylethylene in different solvents
Authors: Hild M. , Brauer H.‐D. 
Published: July 2012

AbstractRate constantskRof the ene reaction of singlet oxygen (1Δg) with tetramethylethylene (TME) have been determined in six solvents with different polarity at elevated pressures up to 1200 bar using time‐resolved phosphorescence technique. Experimental activation volumes, ΔV, resulted in the range between −20.7 cm3· mol−1(in benzonitrile) and −35.1 cm3· mol−1(in n‐hexane). These results were analysed taking into account contact complex formation as the initial step. The reaction volume ΔVcof the formation of the contact complex was evaluated using the statistical model developed by Yoshimura and Nakahara. The data obtained confirm the assumption of a polar intermediate resembling a perepoxide. The intrinsic activation volume ΔVwas found to be −14.5 cm3· mol−1and the dipole moment of the transition state was estimated to be μ≠= 3.4 Debye.