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  • 1
    Digitale Medien
    Digitale Medien
    Beta-delayed gammas and QEC-values in the decays of150m,152mHo and149Dy (1990)
    Springer
    The European physical journal 337 (1990), S. 161-168 
    Details
    ISSN: 1434-601X
    Schlagwort(e): 23.20.Lv ; 23.40.−s ; 27.60.+j ; 27.70.+ q
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract 150m, 152mHo, and149Dy were produced by fusion-evaporation reactions of40Ar with targets of natural indium and114Cd. Theβ-decays of the isotopes were reinvestigated with emphasis on high-excitation daughter states. The decay energies for selectedβ-transitions were measured from electron-capture to positron-decay ratios. Corrections forγ-feeding from higher-lying states were taken into account. The following QEC-values were derived for150mHo,152mHo, and149mDy of 6819 ( −100 +117 , 6263 ( −80 +89 ), and 3914 ( −52 +76 ) keV, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01294287
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  • 2
    Digitale Medien
    Digitale Medien
    Measurements of circular polarization correlations following excitation of Ar and Kr by electron impact (1994)
    Springer
    The European physical journal 30 (1994), S. 115-118 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.80.Dp
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report measurements of the circular polarization correlation parameterP 3 for the excitation of the 4s′[1/2] j=1 state in Ar by 40 eV electrons and for the excitation of the Kr 5s[3/2] J=1 state by 30 eV electrons at electron scattering angles up to 50°. The measured Ar data are compared to predictions of a distorted wave Born approximation (DWBA). The agreement is in general not very good with theory predictingP 3 values considerably larger than the measured values in the regime of small scattering angles. In Kr, where the measured data are compared to theoretical predictions from a DWBA, a first-order many-body theory (FOMBT) and a relativistic distorted wave theory (RDW), the level of agreement between experiment and theory is somewhat better. The measuredP 3 parameters in conjunction with the previously measured linear coherence parametersP 1 undP 2 under the same scattering conditions yield the total polarizationP tot + which is a measure for the level of coherence in the excitation process. In both cases studied here, we found values of eliminateP tot + that were consistent with a fully coherent excitation process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426058
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  • 3
    Digitale Medien
    Digitale Medien
    Electron-photon polarization correlation studies in neon and argon (1992)
    Springer
    The European physical journal 23 (1992), S. 137-144 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.80.Dp
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We studied the electron impact excitation of the (2 P 1/2) ns [1/2] J=1 states in Ne (n=3) and Ar (n=4) using the electron-photon polarization correlation technique. The two linear Stokes' parametersP 1 andP 2 have been measured in Ne at an impact energy of 50 eV and in Ar at 30 eV and 40 eV for electron scattering angles up to 40° (up to 50° in Ar at 40 eV). In addition, previous measurements in Ar at 50 eV have been extended to scattering angles of 40° in an effort to facilitate a more meaningful and broader comparison of the Ar results obtained at different impact energies. Two of the four independent parameters required for a complete description of the excitation process, the alignment angle γ and the linear polarizationP lin + of the angular part of the collisionally induced excited state charge cloud were extracted from theP 1 andP 2 measurements. A comparison with theoretical predictions from first-order perturbative theories such as a distorted-wave Born approximation (DWBA) and a first-order many-body theory (FOMBT) revealed a generally good agreement between experiment and theory in Ne and Ar at 50 eV except for some discrepancies at scattering angles above 30°, whereas the agreement between experiment and theory was much less satisfactory in Ar at 30 eV and at 40 eV over the entire range of scattering angles studies in this work. We found that the measured coherence parameters appear to be shifted systematically towards larger scattering angles compared to the theoretical predictions as the impact energy is decreased.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01436735
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  • 4
    Digitale Medien
    Digitale Medien
    The electron-impact ionization of Ar and Kr revisited: a critical analysis of double-to-single ionization cross section ratio measurements using the fast-atom-beam technique (1992)
    Springer
    The European physical journal 22 (1992), S. 603-610 
    Details
    ISSN: 1434-6079
    Schlagwort(e): 34.80.Dp
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report new measurements of the absolute electron-impact double ionization cross sections for Ar and Kr and of the ratios of double-to-single ionization for impact energies from threshold to 200 eV using the crossed electron-beam — fast-atom-beam technique. The work was motivated by the recently highlighted spread of about 30% in the Ar2+/Ar+ ionization cross section ratios obtained by several groups using different experimental techniques. Such a spread is inconsistent with statistical uncertainties of typically 3% or less that were quoted for the various reported ratios. A similar situation exists for Kr where the spread among the recently published Kr2+/Kr+ ionization cross section ratios is about 15%. We made an attempt to identify all potential systematic errors inherent to the fast-beam technique that could affect the measurement of cross section ratios with special emphasis on those systematic errors that could influence the detection of singly and doubly charged product ions differently. We found Ar2+/Ar+ and Kr2+/Kr+ cross section ratios of, respectively 0.066 ±0.007 and 0.087 ±0.008 at 100 eV which confirm earlier measurements using the same experimental technique. The error limits on cross sections ratios measured in our fast-beam apparatus were determined to be at least ±9% for cross section ratios of multiple-to-single ionization for the same target atom and at least ±10% for ratios of single ionization cross sections for different target species. Our error limits are dominated by systematic uncertainties of the apparatus which do not cancel when cross section ratios are measured, since the ratios are obtained under similar, but not identical experimental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01426361
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