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  • 1995-1999  (3)
  • 1990-1994  (2)
  • 1980-1984  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Electronic rearrangement on molecules accompanyingβ-decay investigated by nuclear resonance fluorescence (1983)
    Springer
    The European physical journal 311 (1983), S. 253-257 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using gaseous60CoI2 sources, the velocity distribution of60Ni nuclei afterβ-decay of60Co has been measured by the nuclear-resonance-fluorescence coincidence (NRFC) method. By comparison with model calculations, information is obtained on the rearrangement of electrons on the molecule as a consequence of the change of nuclear charge. In 42% of the rearrangement processes bound (NiI2)+ or (NiI)+ molecule ions are formed. In 24% the molecule is singly charged but with the bonds between Ni and its molecular partners ruptured. In 34% the charging of more than one molecular partner leads to Coulomb explosion of the molecule. The probability of finding more than one charge on the molecule is larger by a factor of 2 as compared to the probability for electron shake-off on an isolated Ni atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01415678
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Stopping of slow recoil atoms in gases (1981)
    Springer
    The European physical journal 301 (1981), S. 101-107 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Nuclear Resonance Fluorescence spectra contain information on the slowing-down behaviour of recoiling atoms in the energy range pertinent to the specific reaction. On the basis of conventional transport theory, measured spectra for arsenic atoms with energies ≲15 eV slowing down in helium are analysed. The assumption of continuous slowing down turns out to be well justified, and the thermal motion of the gas atoms is shown to influence the effective stopping power only slightly. Somewhat surprising in view of uncertainties concerning the charge state of the recoiling atoms, theoretical predictions based on Lenz-Jensen elastic interaction agree well with the measured spectra. At present, the experimental data do not allow direct inversion, but the calculated spectra are shown to depend sensitively on the stopping-power input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01419238
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of the nuclear recoil motion on the phonon spectrum of solids investigated by nuclear resonance fluorescence (1984)
    Springer
    The European physical journal 55 (1984), S. 287-291 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The time dependence of the recoil velocity of a140Ce nucleus in a La and a LaF3 lattice after β emission is studied via the Doppler shift of the 1.596 MeV γ transition in140Ce. Evidence is obtained that the nucleus does not leave the lattice site even at a recoil energy of about 20 eV but carries out a damped oscillation. The quantitative comparison of the recoil velocity with the predictions of lattice theory leads to partial agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01304079
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The stopping of slow75As recoil atoms in He, Ne and H2 (1982)
    Springer
    The European physical journal 306 (1982), S. 301-306 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The slowing down of75As recoil atoms with energies ≲10eV in He, Ne and H2 was investigated by measuring Doppler-widened line profiles of the 265 keV gamma line emitted by the recoil nuclei. The line profiles contain information on the stopping powers of gases for heavy ions with initial velocities υ≲3·105 cms−1. They are analyzed in terms of the continuous slowing down theory developed by Falcone et al. The profiles observed with He and Ne are well described by assuming the stopping power to be based on Lenz-Jensen elastic interaction between recoil and moderator atoms. The profiles observed with H2 do not agree with predictions based on that interaction. The stopping power of H2 for the75As recoil atoms is found to be larger than that of He.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01432370
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  • 5
    Electronic Resource
    Electronic Resource
    Probing grain boundaries in As-doped polycrystalline silicon (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 383-388 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using 111In–111Cd perturbed angular correlations, we investigated the behaviour of In in heavily As-doped polycrystalline silicon. The nuclear In tracers were either introduced by means of grain boundary (GB) diffusion or ion implantation. We find, that the in-diffused In tracers exclusively probe GBs which give rise to a broad distribution of static quadrupole frequencies. The implanted tracers exclusively probe Si bulk material, where they encounter As-dopants during thermal annealing and form the well-known In–As complexes #1 and #2, and the previously unknown complex #4 (eQVzz=117 MHz, η=0) which involves three As atoms on nearest neighbor sites with respect to the probe. The implications of the present experiment on acceptor doping and GB probing are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017076801985
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure-dependent perturbed directional correlations and collision cross sections in the meV and eV energy region for gaseous ion — Noble gas systems (1983)
    Springer
    Hyperfine interactions 15 (1983), S. 173-176 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Conclusions The new experimental results for pure H 2 75 Se complete the measurements of gaseous H 2 75Se-sources with different buffer gases. The extended theory produces a good fit to all experimental points and provides the foundation for interpreting the estimated collision cross sections as depolarization or charge transfer cross sections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02159734
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Solid solubility of rhodium in silver (1993)
    Springer
    Hyperfine interactions 80 (1993), S. 983-987 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two PAC probes,99Rh and111In, were employed to study the solid solubility of rhodium in silver. The solute rhodium atom concentration was determined for alloys containing 0.1–1.0 at% of Rh. It increases with increasing temperature up to about 0.04 at% at 1200 K and it does not depend essentially on the nominal impurity concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00567451
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    PAC measurements of the Verwey transition in magnetite (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 237-241 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Perturbed angular correlation (PAC) experiments with implanted 111In tracers have recently been used to investigate magnetic phase transitions in metal oxides. Here we report on PAC measurements for 111Cd in polycrystalline Fe3O4 in the neighborhood of the Verwey phase transition (TV≈ 120 K). Perturbed angular correlation spectra were taken for implanted 111In probes at temperatures between 9 and 850 K. The two observed Larmor frequencies are attributed to the two possible cation sites in the cubic inverse spinel lattice. For T 〉 120 K, the temperature dependence of both Larmor frequencies follows a Curie–Weiss power law ωL(T)/ ωL(0)=(1-T/TN)β, with the parameters TN=848(2) K and β= 0.392(2). At the Verwey temperature we find a rapid change of both Larmor frequencies, with ωL1 increasing from 178(2) MHz at 120 K to 191(4) MHz at 100 K, and ωL2 decreasing from 173(4) MHz to 151(5) MHz. The Verwey transition also affects the widths of the frequency distributions, which more or less double below TV. This possibly indicates the presence of several components with Larmor frequencies similar to those found in the previous Mössbauer data, or for electronic after-effects correlated with the semiconductivity of magnetite below TV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017023322941
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    On the observation of intrinsic defects in (Co1-xInx)1-δO by PAC (1999)
    Springer
    Hyperfine interactions 120-121 (1999), S. 439-443 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on the results of Perturbed Angular Correlation measurements in polycrystalline (Co1-xInx)1-δO samples (x = 0.04 and 0.8 at.%) using ion-implanted 111In tracers. The temperature and the oxygen activity (adjusted via a CO/CO2 mixture) were chosen in such a way as to be able to observe defect trapping and detrapping in thermal equilibrium. The results are compared with those obtained for (Co1-xInx)1-δO (x= 0.04 at.%) rapidly cooled to 350 K and for CoO.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017097406528
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Measurement of the hyperfine interaction of free75As ions In H2, He, Ne, Kr and Xe buffer environments and estimate of clolision cross sections in the eV and meV energy region (1983)
    Springer
    Hyperfine interactions 13 (1983), S. 297-305 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the time-integral perturbed angular correlation (TIPAC) method the pressure dependence of the perturbation of the 121.1–279.5 keV γ-γ cascade in75As has been investigated using gaseous H2 75Se sources in different buffer environments. The obtained attenuation coefficients G22 (∞) in the range of 0.55 to 1.0 were fitted with a theoretical stochastic model. In the region of low density, where the correlation time τC is large compared to the lifetime τ of the intermediate level of the nucleus, charge transfer collision cross sections have been evaluated between 8.1·10−16 cm2 for He, 1.3·10−14 cm2 for Xe and 1.8·10−14 cm2 for the molecular H2 buffer gas. For increasing densities of the buffer gases the correlation time τC became small compared to the intermediate lifetime τ. The main effect in this region is the depolarization, and we found cross sections between 5.2·10−15 cm2 for He, 8.7·10−14 cm2 for Xe and 1.2·10−13 cm2 for the H2 buffer gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01027259
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    Paper (German National Licenses)
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