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  • Inorganic Chemistry  (14)
  • 61.70  (5)
  • 14.80.Pb  (2)
  • Atomic, Molecular and Optical Physics  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    The positron beam at the stuttgart pelletron accelerator and its applications toβ +γ positron lifetime measurements (1987)
    Springer
    Applied physics 43 (1987), S. 261-267 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00635181
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of resistance fluctuations independent of thermal voltage noise (1980)
    Springer
    Applied physics 22 (1980), S. 185-187 
    Details
    ISSN: 1432-0630
    Keywords: 06 ; 07 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract New methods for thermal-equilibrium investigations of atomic vacancies or of dislocation movements in metals require measurements of minute resistance fluctuations. The accuracy of such measurements is limited by thermal noise from the resistor. The present paper proposes a method for analysing resistance fluctuations independent of voltage noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00886003
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  • 3
    Electronic Resource
    Electronic Resource
    Vacancy noise measurements in metals: Calculation of the power spectrum (1983)
    Springer
    Applied physics 30 (1983), S. 117-122 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 72.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Fluctuations in the number of vacancies in metals in thermal equilibrium lead to resistivity fluctuations. Analysis of these fluctuations permits measurement of both formation and migration enthalpy of the vacancies. The power spectrum of the fluctuations is calculated using a series of statistically independent pulses. It can be derived from the diffusion equation for any geometry of the vacancy sinks. Vacancy diffusion to the surface of a thin plate or of a sphere are treated as examples. The measurability of vacancy noise is assessed. It should also be possible to measure vacancy noise during irradiation. It is predicted that correlated vacancy creation, which may occur during irradiation, will cause an increase in the power spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614913
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  • 4
    Electronic Resource
    Electronic Resource
    Positron lifetimes and annihilation lineshape in Cd and au from 4.2 K to the melting points (1977)
    Springer
    Applied physics 12 (1977), S. 59-67 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of an integrated source-specimen technique the temperature dependence of positron lifetimes and annihilation lineshapes has been measured, on the same specimens of gold and cadmium from 4.2K to the melting points, and also in electronirradiated and quenched gold. The anomalous temperature dependence of positron annihilation at intermediate temperatures (200 to 350 K in Cd, 270 to 750 K in Au) discovered by Lichtenberger, Schulte, and MacKenzie is confirmed. The data are incompatible with the idea that the intermediate temperature dependence is due to thermal expansion. They are well explained by an extension of the trapping model which includes the formation of metastable self-trapped positrons. From lineshape measurements after electron irradiation at 180 K and after quenching it is deduced that the trapping rate of positrons at vacancy-type defects in Au is temperature independent below room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900069
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  • 5
    Electronic Resource
    Electronic Resource
    A novel technique for measuring resistance fluctuations independently of background noise (1989)
    Springer
    Applied physics 48 (1989), S. 233-236 
    Details
    ISSN: 1432-0630
    Keywords: 06 ; 07 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A novel method is presented for measuring the spectral density of resistance fluctuations without the explicit determination of the voltage background noise (Johnson noise, pre-amplifier noise). The output of a standard ac bridge excited by a single-frequency alternating current is demodulated by two phase-sensitive detectors which operate in quadrature. When the phase difference between excitation and detection is properly set, the real part of the cross-spectral density of the two demodulators shows only the spectral density of the resistance fluctuations and not the disturbing background noise. The feasibility of our new method is demonstrated by measurements of 1/f noise of a thin-film A1 sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619390
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence for a resonance in positron-electron scattering at 810 keV centre-of-mass Energy (1988)
    Springer
    The European physical journal 330 (1988), S. 173-181 
    Details
    ISSN: 1434-601X
    Keywords: 13.10.+q ; 12.20.Fv ; 14.80.Pb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A monoenergetic positron (e +) beam (ΔT/T〈5·10−4) from the Stuttgart pelletron accelerator and a 4.6 mg/cm2 Be target has been employed to investigatee + e −scattering in the MeV region in a large solid angle with high statistics by means of a novel positionsensitive detector system. Superimposed on the Bhabha scattering, a structure has been found at ane + kinetic energy of 2263 keV (810 keV excitation energy in thee + e −rest frame). From the energy-integrated resonance cross-section of $$\sigma _{res} \cdot \Gamma _{res}^{e^ + e^ - } $$ ≅30 b·eV (c.m.) and the standard resonance cross-section we estimate partial resonance widths $$\Gamma _{res}^{e^ + e^ - } $$ ≅72 meV or 24 meV for total angular momenta J=0 or J=1, respectively. The structure, which has not been predicted within the framework of quantum electrodynamics, coincides with one of the sum energies of the correlatede + e −lines observed in heavy-ion collisions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01293393
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  • 7
    Electronic Resource
    Electronic Resource
    Limits for two-photon ande + e − decay widths of positron-electron scattering resonances for√s=1.78 to 1.92 MeV (1991)
    Springer
    The European physical journal 340 (1991), S. 209-218 
    Details
    ISSN: 1434-601X
    Keywords: 14.80.Pb ; 13.10. + q ; 12.20.Fv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Motivated by the observation of energy- and momentum-correlatede + e − pairs in heavy ion collisions, a search for resonances ine + e − scattering at the corresponding energies has been made. Thee + e − decay channel is analyzed in a time window from ∼ 10−13 s to ∼ 10−11 s with a set-up optimized for low-background detection of delayede + e − decays. The two-photon decay channel of a hypothetical resonance is investigated by measuring the two-photon annihilation-in-flight excitation function. New upper limits for the partiale + e − decay width Γee of a few meV are derived for total centre-of-mass energies √s between 1.78 and 1.92 MeV, taking into account the dilepton as well as the two-photon decay of a neutral resonance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01303834
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  • 8
    Electronic Resource
    Electronic Resource
    Darstellung und Schwingungsspektrum von Tetrathiomethyl-phosphonium-hexachloroantimonatFrau Professor Margot Becke-Goehring zum 60. Geburtstage gewidmet (1974)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 406 (1974), S. 307-311 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Vibrational Spectrum of Tetra-thiomethyl-phosphoniuin-hexachloroantimonatePreparation, properties and vibrational spectrum of Tetra-thiomethyl-phosphonium-hexachloroantimonate are reported. The kind of bonding in the ion is brief discussed.
    Notes: Es wird über die Darstellung, Eigenschaften und Schwingungsspektren des Tetra-thiomethyl-phosphonium-hexachloroantimonats berichtet. Die Bindungsverhältnisse werden kurz diskutiert.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19744060225
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  • 9
    Electronic Resource
    Electronic Resource
    Über das Fluoreszenzthermochrome Acetonitrilo-Kupferjodid mit Dibenzo-18-Krone-6 (1978)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 442 (1978), S. 221-224 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: About the Fluorescence Thermochromism of Acetonitrile Copper Iodide with Dibenzo-18-Crown-6Copper iodide reacts in actonitrile solution with dibenzo-18-crown-6 to form a compound,(CuJ)4(CH3CN)4(db-18-c-6), which fluoresces yellow at 298K, but pink at 77 K. It decomposes at 55.3°C. (5 Torr) by lost of acetonitrile and a heterogeneous mixture of copper iodide and polyether results. In absence of dibenzo-18-crown-6, copper iodide forms with acetonitrile a heterogeneous mixture of copper iodide and polyether results. In absence of dibenzo-18-crown-6, copper iodide forms with acetonitrile a solvate CuJ. CH3CN. It also shows fluorescence thermochromism (yellow at 298 K, but green at 77 k) but decomposes at 0°C and 760 Torr.The luminescences pectra of the macrocyclic polyether complex at 298 K is redshifted. This probably results from intersection between the crown and the acetonitrile copper iodide.
    Notes: Kupferjodid bildet in Acetonitril mit Dibenzo-18-Krone-6 eine Verbindung der Zusammensetzung (CuJ)4(CH3CN)4(db-18-c-6), die bei Raumtemperatur gelb, bei 77K rosa fluoresziert. Sie zersetzt sich bei 55,3°C (5 Torr) unter Verlust von Acetonitril zu einem heterogenen Gemenge aus Kronenäther Kupferjodid.In Abwesenheit von Kronenäther bildet Kupferjodid in Acetonitril ein Solvat CuJ · CH3CN. Es ist ebenfalls fluoreszenzthermochrom (gelb bei 298 K, grün bei 77 K) und zersetzt sich allerdings schon bei 0°C( 760 Torr). Das Lumineszenzspektrum des makrocyclischen Polyätherkomplexes ist bei 298 K rotverschoben, was wahrscheinlich auf die Wechselwirkung des Kronenäthers mit dem Acetonitrilo-Kupferjodid zurückzuführen ist.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19784420129
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  • 10
    Electronic Resource
    Electronic Resource
    Schwingungsspektren und Kraftkonstanten der Übergangsreihen OPF3 - OP(CH3)3 und SPF3 - SP(CH3)3 (1972)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 389 (1972), S. 269-279 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The vibration spectra (IR and RAMAN) are reported for OPF2(CH3), OPF(CH3)2, SPF2(CH3), SPF(CH3)2 and SPF2(C2H5) and assigned to the normal vibrations. For these compounds all valence force constants are calculated by a simplified valence force field. Substitution of fluorine atoms by the methyl group causes a diminuation of all force constants. There is a clear difference between Δf P—CH3 (- 18%) and Δf X =P and Δf P—F (-30%). The P—CH3 bond is incapable to form dπ—pπ-bonds. Therefore the diminuation of f P—CH3 is caused only by the inductive effect.
    Notes: Von OPF2(CH3), OPF(CH3)2, SPF2(CH3), SPF(CH3)2 und SPF2(C2H5) werden die Schwingungsspektren (meistens IR und RAMAN) mitgeteilt und den Grundschwingungen zugeordnet. Gemeinsam mit den Endgliedern XPF3 und XP(CH3)3 (X = O, S) werden die Valenzkraftkonstanten nach einem Näherungsverfahren berechnet. Sämtliche Kraftkonstanten nehmen beim Ersatz von Fluor durch die Methylgruppe stark ab. Für f P—CH3 (-18%) ergibt sich gegenüber f P = X und f P—F (-30%) ein deutlicher Unterschied, bedingt durch die Unfähigkeit der CH3-Gruppe zur Ausbildung von dπ—pπ-Bindungen. Die Abnahme für f P—CH3 wird auf den induktiven Effekt allein zurückgeführt.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19723890307
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