STATISTICAL CALCULATION OF THE DENSITY OF DOORWAY STATES AND ON THE PROBLEMS OF THEIR EXPERIMENTAL DETECTION. (in German)
Journal Article
·
· Oesterr. Akad. Wiss., Math.-Naturwiss. Kl., Sitzungsber., Abt. II 176: 245-52(1967).
OSTI ID:4009383
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-25-043991
- OSTI ID:
- 4009383
- Journal Information:
- Oesterr. Akad. Wiss., Math.-Naturwiss. Kl., Sitzungsber., Abt. II 176: 245-52(1967)., Other Information: Orig. Receipt Date: 31-DEC-71
- Country of Publication:
- Country unknown/Code not available
- Language:
- German
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THE STATISTICAL CALCULATION OF THE DENSITY OF DOORWAY STATES AND THE PROBLEM OF THEIR EXPERIMENTAL DETECTION.
Most theoretical approaches used in nuclear astrophysics to model the nucleosynthesis of heavy elements incorporate the so-called statistical model in order to describe the excitation and decay properties of atomic nuclei. One of the basic assumptions of this model is the validity of the Brink–Axel hypothesis and the related concept of so-called photon strength functions to describe γ-ray transition probabilities. We present a novel experimental approach that allows for the first time to experimentally determine the photon strength function simultaneously in two independent ways by a unique combination of quasi-monochromatic photon beams and a newly implemented γ–γ coincidence setup. This technique does not assume a priori the validity of the Brink–Axel hypothesis and sets a benchmark in terms of the detection sensitivity for measuring decay properties of photo-excited states below the neutron separation energy. The data for the spherical off-shell nucleus 128Te were obtained for γ-ray beam-energy settings between 3 MeV and 9 MeV in steps of 130 keV for the lower beam energies and in steps of up to 280 keV for the highest beam settings. We present a quantitative analysis on the consistency of the derived photon strength function with the Brink–Axel hypothesis. The data clearly demonstrate a discrepancy of up to a factor of two between the photon strength functions extracted from the photoabsorption and photon emission process, respectively. In addition, we observe that the photon strength functions are not independent of the excitation energy, as usually assumed. Thus, we conclude, that the Brink–Axel hypothesis is not strictly fulfilled in the excitation-energy region below the neutron separation threshold (Sn = 8.78 MeV) for the studied case of 128Te.
Doorway states and nuclear-spectrum statistics
Journal Article
·
Mon Jan 01 00:00:00 EST 1968
· Oesterr. Akad. Wiss., Math.-Naturwiss. Kl., Sitzungsber. Abt. II, 176: 245-52(1968).
·
OSTI ID:4009383
Most theoretical approaches used in nuclear astrophysics to model the nucleosynthesis of heavy elements incorporate the so-called statistical model in order to describe the excitation and decay properties of atomic nuclei. One of the basic assumptions of this model is the validity of the Brink–Axel hypothesis and the related concept of so-called photon strength functions to describe γ-ray transition probabilities. We present a novel experimental approach that allows for the first time to experimentally determine the photon strength function simultaneously in two independent ways by a unique combination of quasi-monochromatic photon beams and a newly implemented γ–γ coincidence setup. This technique does not assume a priori the validity of the Brink–Axel hypothesis and sets a benchmark in terms of the detection sensitivity for measuring decay properties of photo-excited states below the neutron separation energy. The data for the spherical off-shell nucleus 128Te were obtained for γ-ray beam-energy settings between 3 MeV and 9 MeV in steps of 130 keV for the lower beam energies and in steps of up to 280 keV for the highest beam settings. We present a quantitative analysis on the consistency of the derived photon strength function with the Brink–Axel hypothesis. The data clearly demonstrate a discrepancy of up to a factor of two between the photon strength functions extracted from the photoabsorption and photon emission process, respectively. In addition, we observe that the photon strength functions are not independent of the excitation energy, as usually assumed. Thus, we conclude, that the Brink–Axel hypothesis is not strictly fulfilled in the excitation-energy region below the neutron separation threshold (Sn = 8.78 MeV) for the studied case of 128Te.
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Doorway states and nuclear-spectrum statistics
Journal Article
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Sat Aug 11 00:00:00 EDT 1973
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