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  • 1985-1989  (25)
  • 1
    Electronic Resource
    Electronic Resource
    Low energy charge exchange cross sections between sodium and H+, H+2, H+3, N+2, H2O+, and O+2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2321-2323 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We confined ions of different molecules in a Penning quadrupole ion trap and observed the exponential loss of the stored ion cloud as the result of charge exchange collisions with a Na atomic beam passing through the trap. From the ion loss rates and the Na density we determined the charge exchange cross sections between Na and the ions noted in the title at a mean ion energy of 2 eV. The results are in reasonable agreement with theoretical expectations and other experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457039
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  • 2
    Electronic Resource
    Electronic Resource
    Temperature dependence of slow-positron production and of positronium formation on untreated surfaces (1987)
    Springer
    Applied physics 44 (1987), S. 105-106 
    Details
    ISSN: 1432-0630
    Keywords: 07.77 ; 29.25
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Low-energy positron emission from tungsten moderators, placed at a electron accelerator beam stop slows down with increasing moderator temperature. Efficient positronium formation is reported on untreated and unoriented metal surfaces at higher target temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626408
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  • 3
    Electronic Resource
    Electronic Resource
    Precision spectroscopy on trapped atomic ions (1987)
    Springer
    Hyperfine interactions 38 (1987), S. 699-709 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent examples of lifetime measurements, ground state hyperfine splittings and spectroscopy on minute samples of radioactive ions illustrate the extension of classical methods of spectroscopy to new regions of interest by the use of ion storage techniques. Estimates are given on the sensitivity of the method with respect to be possible investigation of the Bohr-Weisskopf effect in isotopic chains of elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02394869
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  • 4
    Electronic Resource
    Electronic Resource
    Spin dependence of low energy charge exchange between H 2 + and Na (1987)
    Springer
    The European physical journal 7 (1987), S. 189-192 
    Details
    ISSN: 1434-6079
    Keywords: 34.70 ; 82.30. Fi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The difference in charge exchange rate in collisions between spin oriented sodium atoms and H 2 + ions has been measured at an energy of about 1 eV. H 2 + was stored in a Penning trap and polarized by spin exchange with Na beam atoms from a hexapole magnet. The ion loss from the trap due to charge exchange was different as we depolarized the atomic beam. From the data we obtain a ratio of cross sections for singlet and triplet collisionsQ 1/Q 3=1.5±0.2 andQ 3=1.2·10−15 cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01384587
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  • 5
    Electronic Resource
    Electronic Resource
    Electro-produced slow positrons (1989)
    Springer
    Hyperfine interactions 44 (1989), S. 151-166 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the last 6 years it has been demonstrated that electro-produced intense beams of slow positrons are possible. High energy electrons from an accelerator generate bremsstrahlung in a thick conversion target of high element number Z. The photons produce electronpositron pairs and a small fraction of the positrons may be moderated to thermal energies. A review is given of the existing slow positron beam lines using this technique. At accelerator energies of 100 MeV total conversion efficiencies of several slow positrons per 106 primary electrons have been obtained, resulting in average intensities of several 109 slow positrons per second or more than 105 slow positrons in pulses having a duration of a few ns. A further increase in intensity by at least one order of magnitude seems possible at higher accelerator energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02398666
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of the ground state hyperfine splitting in207Pb II (1988)
    Springer
    The European physical journal 9 (1988), S. 265-265 
    Details
    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ground state hyperfine splitting of simply ionized lead has been determined using pulsed laser excitation of electrodynamically confined ions. We obtain ΔV(6P1/2)=12.85(10) GHz
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438299
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  • 7
    Electronic Resource
    Electronic Resource
    Lifetime of the metastable 6P 3/2 level of PbII (1989)
    Springer
    The European physical journal 11 (1989), S. 283-286 
    Details
    ISSN: 1434-6079
    Keywords: 32.50 ; 32.70.Fw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Pb+-ions were stored in a r.f.-quadrupole trap. Short laser pulses at a 710-nm M1-transition excited the ions to the metastable 6P 3/2 level. Time-resolved registration of the subsequent decay photons at the same wavelength directly gives the lifetime of that state. No dependence of the decay rate on the density of different buffer gases up to 10−5 mbar pressure was observed and from this we deduced upper limits to the quenching cross section. We have observed, however, a small dependence on the stored ion number. The final result for the lifetime is 41.2 ± 0.7 ms in agreement with the result of a previous calculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438500
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  • 8
    Electronic Resource
    Electronic Resource
    Collisional de-excitation of the metastableD-states of Ba+ by He, Ne, N2 and H2 (1989)
    Springer
    The European physical journal 11 (1989), S. 301-304 
    Details
    ISSN: 1434-6079
    Keywords: 34.50-s
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The rate constants 〈σ · υ〉 for collisional de-excitation of the metastable 5D states of Ba+ ions have been determined in an ion trap experiment. TheD-states are selectively populated by pulsed laser excitation of the 6P 1/2 or 6P 3/2 state and the decay at different background pressures is monitored by the change in fluorescence intensity of the excited ions. From the pressure dependence of the decay constants we calculate the de-excitation rate constants for different collision partners, averaged over the velocity distribution of the trapped ion cloud. For He, Ne, H2 and N2 we obtain in the c.m. energy range of 0.1–0.5 eV: 〈σ·υ〉 (He)=3.0±0.2·10−13cm3/s, 〈σ·υ〉 (Ne)=5.1±0.4·10−13cm3/s, 〈σ·υ〉 (H2)=3.7±0.3·10−11cm3/s, 〈σ·υ〉 (N2)=4.4±0.3·10−11cm3/s. The results can be understood qualitatively by a consideration of the ion-atom and ion-molecules interaction potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01438503
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  • 9
    Electronic Resource
    Electronic Resource
    Lifetime and collisional depopulation of the metastable 5D 3/2-state of Yb+ (1988)
    Springer
    The European physical journal 8 (1988), S. 235-237 
    Details
    ISSN: 1434-6079
    Keywords: 32.50 ; 32.70.Fw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The lifetime and collisional depopulation rates of the metastable 5D 3/2 state of Yb+ have been determined in a radiofrequency ion trap by observation of the fluorescence count rate after ion excitation by a short laser pulse. From measurements using He, N2 and H2 as buffer gases between 10−8 and 10−6 mbar pressure and linear extrapolation to zero pressure we obtain a lifetime of τ=52.15±1.00 ms and rate constants ofR(H2)=(1.02±0.10)×10−9 cm3/s andR(N2)=(1.78±0.19)×10−10 cm3/s. The lifetime is in fair agreement with a calculated value of 74 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436946
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  • 10
    Electronic Resource
    Electronic Resource
    Lifetime of the 4D 3/2 and 4D 5/2 metastable states in Sr II (1987)
    Springer
    The European physical journal 5 (1987), S. 97-99 
    Details
    ISSN: 1434-6079
    Keywords: 32.20 ; 32.50 ; 34.90
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Sr+ ions were confined in a r.f. quadrupole trap for times of the order of 30 min. The metastable 4D states were populated via laser excitation of the 5P states. The weak quadrupole transition rate into the 5S 1/2 ground state at 674 and 687 nm was deduced from observation of the exponential decay. At background pressures above 10−7 mbar the radiative decay is dominated by collisional quenching. Extrapolation of the observed decay rate to zero background pressure yields the radiative lifetimes. At pressures around 10−6 mbar fine structure mixing collisions between the 4D states have been observed, which lead to corrections of the extrapolated lifetimes. As the final result we obtain 395±38 ms for 4D 3/2 and 345±33 ms for 4D 5/2. These results are somewhat higher than theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436883
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