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Magnetic dipole and Gamow–Teller modes: quenching, fine structure and astrophysical implications

Richter, A. (2005)
Magnetic dipole and Gamow–Teller modes: quenching, fine structure and astrophysical implications.
In: Journal of Physics: Conference Series, 20
doi: 10.1088/1742-6596/20/1/003
Article, Bibliographie

This is the latest version of this item.

Abstract

The magnetic dipole (M1) and Gamow–Teller (GT) response are prime examples to illustrate the importance of configuration mixing for an understanding of elementary excitation modes of the nucleus. Starting from the ’’classical’’ problem of quenching - whose proper description is still beyond the capabilities of microscopic models after all those years — I want to address some current developments of the field. Mandatory for the progress are high-resolution data from electron and hadron scattering and charge-exchange reactions.

In medium-mass fp-shell nuclei, the detailed knowledge of the M1 and GT strength distribution provides a stringent test of state-of-the-art shell-model calculations, validating their applicability in astrophysical network calculations. As an example, it is demonstrated that high-precision M1 data on N = 28 isotones from electron scattering at Darmstadt permit the extraction of neutral-current neutrino-nucleus scattering cross sections important for supernova dynamics and nucleosynthesis.

Fine structure of the GT mode is not only observed in light and medium-mass nuclei, but also in the GT resonance observed in a heavy nucleus like ⁹⁰Nb studied in the ⁹⁰Zr(³He, t) reaction at Osaka with a resolution ΔE ≃ 50 keV (FWHM). Novel methods, based on wavelet transforms, to extract scales characterizing the fine structure are presented. This in turn permits an interpretation of the physics underlying the phenomenon. These methods can also be used to extract spin- and parity-resolved level densities in a nearly model-independent way, again important to test models used in various astrophysical scenarios.

As a final example, the influence of configuration mixing on the GT strength distribution at low energies is investigated for the heavy odd-odd nuclei ¹³⁸La and ¹⁸⁰Ta. The nucleosynthesis of these exotic nuclides, amongst the rarest in nature, is a long-standing problem. A likely source are charged-current neutrino-nucleus reactions which would be dominated by the GT response. However, the main GT resonance lies above the particle threshold and, therefore, does not contribute. Recent measurements of the GT strength distributions in ¹³⁸La and ¹⁸⁰Ta below the particle threshold and their astrophysical implications are discussed.

Item Type: Article
Erschienen: 2005
Creators: Richter, A.
Type of entry: Bibliographie
Title: Magnetic dipole and Gamow–Teller modes: quenching, fine structure and astrophysical implications
Language: English
Date: July 2005
Place of Publication: Bristol
Publisher: IOP Science
Journal or Publication Title: Journal of Physics: Conference Series
Volume of the journal: 20
DOI: 10.1088/1742-6596/20/1/003
Corresponding Links:
Abstract:

The magnetic dipole (M1) and Gamow–Teller (GT) response are prime examples to illustrate the importance of configuration mixing for an understanding of elementary excitation modes of the nucleus. Starting from the ’’classical’’ problem of quenching - whose proper description is still beyond the capabilities of microscopic models after all those years — I want to address some current developments of the field. Mandatory for the progress are high-resolution data from electron and hadron scattering and charge-exchange reactions.

In medium-mass fp-shell nuclei, the detailed knowledge of the M1 and GT strength distribution provides a stringent test of state-of-the-art shell-model calculations, validating their applicability in astrophysical network calculations. As an example, it is demonstrated that high-precision M1 data on N = 28 isotones from electron scattering at Darmstadt permit the extraction of neutral-current neutrino-nucleus scattering cross sections important for supernova dynamics and nucleosynthesis.

Fine structure of the GT mode is not only observed in light and medium-mass nuclei, but also in the GT resonance observed in a heavy nucleus like ⁹⁰Nb studied in the ⁹⁰Zr(³He, t) reaction at Osaka with a resolution ΔE ≃ 50 keV (FWHM). Novel methods, based on wavelet transforms, to extract scales characterizing the fine structure are presented. This in turn permits an interpretation of the physics underlying the phenomenon. These methods can also be used to extract spin- and parity-resolved level densities in a nearly model-independent way, again important to test models used in various astrophysical scenarios.

As a final example, the influence of configuration mixing on the GT strength distribution at low energies is investigated for the heavy odd-odd nuclei ¹³⁸La and ¹⁸⁰Ta. The nucleosynthesis of these exotic nuclides, amongst the rarest in nature, is a long-standing problem. A likely source are charged-current neutrino-nucleus reactions which would be dominated by the GT response. However, the main GT resonance lies above the particle threshold and, therefore, does not contribute. Recent measurements of the GT strength distributions in ¹³⁸La and ¹⁸⁰Ta below the particle threshold and their astrophysical implications are discussed.

Identification Number: Artikel-ID: 13
Additional Information:

CORRELATION DYNAMICS IN NUCLEI (CDN05) 31 January–4 February 2005, University of Tokyo, Japan

Divisions: DFG-Collaborative Research Centres (incl. Transregio)
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
05 Department of Physics
05 Department of Physics > Institute of Nuclear Physics
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 634: Nuclear Structure, Nuclear Astrophysics and Fundamental Experiments at Low Momentum Transfer at the Superconducting Darmstadt Accelerator (S-DALINAC)
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 634: Nuclear Structure, Nuclear Astrophysics and Fundamental Experiments at Low Momentum Transfer at the Superconducting Darmstadt Accelerator (S-DALINAC) > A: Kernstrukturphysik
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 634: Nuclear Structure, Nuclear Astrophysics and Fundamental Experiments at Low Momentum Transfer at the Superconducting Darmstadt Accelerator (S-DALINAC) > A: Kernstrukturphysik > A2: Kernstrukturphysik mit virtuellen Photonen
Date Deposited: 20 Jun 2011 07:12
Last Modified: 01 Mar 2024 09:21
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