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  • 1985-1989  (25)
  • 1965-1969  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2321-2323 
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 222 (1969), S. 201-207 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown that a previously described method for measuring the spin resonance of free electrons in a trap can also be used to measure their (g-2) anomaly. The electrons are trapped in an electrostatic quadrupole field with a superimposed homogeneous axial magnetic field, and are polarized by spin exchange. The spin and (g-2) resonance are monitored through the spin dependence of the excitation processe+Na (3S)→e+Na(3P). Calculations are made of the energy levels and transition probabilities of the trapped electrons.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 183 (1965), S. 223-233 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An electric molecular beam resonance spectrometer has been used to measure simultaneously the Zeeman- and Stark-effect splitting of the hyperfine structure of23Na19F. Electric four pole lenses served as focusing and refocusing fields of the spectrometer. A homogenous magnetic field (Zeeman field) was superimposed to the electric field (Stark field) in the transition region of the apparatus. The observed (Δm J=±1)-transitions were induced electrically. Completely resolved spectra of NaF in theJ=1 rotational state have been measured in several vibrational states. The obtained quantities are: The electric dipolmomentμ el of the molecule forv=0, 1 and 2, the rotational magnetic dipolmomentμ J forv=0, 1, the difference of the magnetic shielding (σ ⊥-σ ‖) by the electrons of both nuclei as well as the difference of the molecular susceptibility (ξ ⊥-ξ ‖), the spin rotational constantsc F andc Na, the scalar and the tensor part of the molecular spin-spin interaction, the quadrupol interactione q Q forv=0, 1 and 2. The numerical values are $$\begin{gathered} \mu _{\mathfrak{e}1} = 8,152(6) deb \hfill \\ \frac{{\mu _{\mathfrak{e}1} (v = 1)}}{{\mu _{\mathfrak{e}1} (v = 0)}} = 1,007985 (7) \hfill \\ \frac{{\mu _{\mathfrak{e}1} (v = 2)}}{{\mu _{\mathfrak{e}1} (v = 1)}} = 1,00798 (5) \hfill \\ \mu _J = - 2,89(3)10^{ - 6} \mu _B \hfill \\ \frac{{\mu _J (v = 0)}}{{\mu _J (v = 1)}} = 1,020 (13) \hfill \\ (\sigma _ \bot - \sigma _\parallel )_{Na} = - 51(12) \cdot 10^{ - 5} \hfill \\ (\sigma _ \bot - \sigma _\parallel )_F = - 51(12) \cdot 10^{ - 6} \hfill \\ (\xi _ \bot - \xi _\parallel ) = - 1,59(120)10^{ - 30} erg/Gau\beta ^2 \hfill \\ {}^CNa/^h = 1,7 (2)kHz \hfill \\ {}^CF/^h = 2,2 (2)kHz \hfill \\ {}^dT/^h = 3,7 (2)kHz \hfill \\ {}^dS/^h = 0,2 (2)kHz \hfill \\ eq Q/h = - 8,4393 (19)MHz \hfill \\ \frac{{eq Q(v = 0)}}{{eq Q(v = 1)}} = 1,0134 (2) \hfill \\ \frac{{eq Q(v = 1)}}{{eq Q(v = 2)}} = 1,0135 (2) \hfill \\ \end{gathered} $$ The quantities in brackets are three times the root-mean-square deviations in units of the last digit. From these data a number of expressions are derived which characterise the electronic charge distribution in the molecule.
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  • 4
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 11 (1989), S. 301-304 
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 11 (1989), S. 283-286 
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 7 (1987), S. 189-192 
    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.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 8 (1988), S. 235-237 
    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.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 5 (1987), S. 97-99 
    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.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 9 (1988), S. 265-265 
    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
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