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  • 1
    Electronic Resource
    Electronic Resource
    ‘Slow’ residues observed in the reaction20Ne+208Pb at E/A=8.6, 11.4 and 15.0 MeV/u (1994)
    Springer
    The European physical journal 348 (1994), S. 301-309 
    Details
    ISSN: 1434-601X
    Keywords: 25.70.Gh ; 25.70.Jj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Velocity distributions of heavy residuesA Res〉A tar,Z Res〉Z tar identified by means ofα spectroscopy, have been investigated at the velocity filter SHIP in reactions20Ne+208Pb at projectile energies E/A=8.6, 11.4 and 15.0 MeV/u. Besides products from complete or nearly complete fusion, characterized by velocity distributions peaking atν/ν CN≅0.8–1.0, heavy residues with mean velocities of about half of the compound nucleus velocity were observed. The Z-distribution of this component was found to peak atZ=87. It is interpreted as residues from fusion of target nuclei with projectile fragments produced by nearly symmetric break-up. The experimental results were compared with predictions of theoretical models: cross sections for incomplete fusion were calculated using the sum-rule model of Wilcynski et al., while residue cross sections were calculated using the evaporation code HIVAP. A fair agreement between experimental and calculated mass distributions of heavy residues and transferred projectile fragments is achieved if an energy dissipation of ≅23% (at E/A=8.6 MeV/u) and ≅8% (at E/A=11.4 MeV/u) of the incident projectile energy is introduced. The observed peak of theZ-distribution atZ=87 is predominantly effected due to a higher fission probability of products withZ〉87 during the deexcitation process and experimental limitations in the identification of products withZ≦86 by means of a spectroscopy, which cause a decrease of the observed production rates towards lowerZ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01305889
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  • 2
    Electronic Resource
    Electronic Resource
    Rheological behavior and birefringence investigations on drag-reducing surfactant solutions of tallow-(tris-hydroxyethyl)-ammonium acetate/sodiumsalicylate mixtures (1994)
    Springer
    Rheologica acta 33 (1994), S. 419-430 
    Details
    ISSN: 1435-1528
    Keywords: Shear-induced micellar structures ; flow birefringence ; dragreducing surfactant solutions ; mixed surfactant systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Rheological and flow birefringent properties of a drag-reducing mixture of tallow-(tris-hydroxiethyl)-ammonium acetate (ETHOQUAD T/13-50) and sodiumsalicylate (NaSal) have been studied as a function of the concentration and of the salt/surfactant molar ratio x. The optimum molar ratio x for drag reduction is around 2.5. It is shown that shear-induced supramicellar structures (SIS) which are believed to be responsible for friction reduction in turbulent pipe flow develop in the presence of NaSal. It was observed that SIS are also formed even if the concentration c exceeds c *, i.e., the concentration where the volumes of rotation of the individual rodlike micelles start to overlap. The validity of the stress optical law is discussed. A switch from a reptation-controlled stress relaxation to a kinetically controlled mechanism takes place at x ≈ 2.5 for this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366584
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  • 3
    Electronic Resource
    Electronic Resource
    Lamb-Mössbauer factor in the spin crossover compound Fe(tpa)(NCS)2 (1994)
    Springer
    Hyperfine interactions 93 (1994), S. 1459-1463 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Lamb-Mössbauer factor in spin crossover compounds has been the subject of controversial discussions in the literature. For several compounds, a significantly larger Lamb-Mössbauer factor for the complex molecules in the low-spin (f ls) than in the high-spin (f hs) state has been reported, while for compounds studied in our laboratory such differences could not be observed. We prepared the compound Fe(tpa)(NCS)2, thef factors of which were reported to be very different. We could not prove thef factors of this compound to be different. The implications of a different structural phase of compound prepared by us are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02072893
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  • 4
    Electronic Resource
    Electronic Resource
    Depth profiling with sample rotation: Capabilities and limitations (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 304-309 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Depth profiling with sample rotation has become a frequently applied method to obtain the in-depth distribution of composition in thin films with high resolution. Sample rotation strongly diminishes the effect of local variations of the ion beam intensity and of the sputtering yield, which are the main cause of increasing surface roughness during sputtering and therefore of profile broadening. Capabilities and limitations of rotational profiling are considered with respect to its dependence on various parameters, such as inhomogeneity of the ion beam instensity, ion incidence angle and rotation speed. In particular, it is shown that non-linear components and excentric movement of the sample lead to periodic features in the profile and to non-vanishing degradation of depth resolution with depth. For smooth sample surfaces, depth resolution improves with increasing ion incidence angle but is much less pronounced, as for profiling with stationary samples. For originally rough surfaces, the deterioration of depth resolution with increasing ion incidence angle is considerably reduced. The key parameter for optimized conditions in rotational profiling is the ratio of sputtering rate and rotation speed. The minimum necessary, useful rotation speed depends on this ratio and on the magnitude of other contributions to the depth resolution that are not affected by sample rotation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210507
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  • 5
    Electronic Resource
    Electronic Resource
    Interfacial reactions and silicide formation in Si/Ni/Si and Si/Cr/Si sandwich layersPaper presented at ECASIA 93, Catania, Sicily, 4-8 October 1993. (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 560-565 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The preparation of well-characterized silicide thin films for microelectronics needs a control of interfacial reactions and diffusion processes during heat treatment of metal/semiconductor systems. Two sandwich structures of Si(33 nm)/Me(50 nm)/Si(33 nm), where Me = Ni or Cr, with a total thickness of each structure of 116 nm were sputter deposited onto smooth silicon-(111) substrates. The reactions of both metals with amorphous silicon thin films were activated in a differential scanning calorimeter (DSC), at a heating rate of 40°C/min-1, between room temperature and different higher temperatures. Auguer electron spectroscopy depth profiles showed that the Si/Ni/Si sandwich structure reacted almost completely during heat treatment up to 320°C and formed reaction products with a composition close to Ni3Si2. Selected area diffraction patterns revealed that this is a mixture of Ni2Si and NiSi silicides. A much less pronounced reaction between Si and Cr was observed in the Si/Cr/Si sandwich structure, even with heating to 630°C, resulting in CrSi2 silicide and different Cr-Si solid solutions. The results of AES depth profiling studies of the thermally treated sandwich structures are discussed in terms of diffusion processes, movement of interfaces and formation of silicides. The additional information obtained with differential scanning calorimetry and transmission electron microscopy enables a detailed identification of reaction products formed in the early stage of the thermally treated Si/Me/Si structures.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740210808
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    Paper (German National Licenses)
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