https://doi.org/10.1140/epja/s10050-023-01067-8
Letter
Brink-Axel hypothesis in the pygmy-dipole resonance region
1
Université de Strasbourg, IPHC, 23 rue du Loess, 67037, Strasbourg, France
2
CNRS, UMR7178, 67037, Strasbourg, France
Received:
19
June
2023
Accepted:
22
June
2023
Published online:
5
July
2023
The Brink–Axel hypothesis, which states that the photoabsorption cross section is independent of the excitation energy of a nuclear system, is an assumption used in nuclear structure studies and calculations of neutron-capture cross section for astrophysical applications. In the present work, using microscopic Configuration Interaction method, it is demonstrated that the dipole photoabsorption cross section at low energy is dependent on the excitation energy and deviations from the Brink-Axel hypothesis are particularily large for the ground state of an even-even system. It is also shown that the low-lying E1-strength, known as pygmy dipole resonance, is redistributed with the excitation energy of the initial state and strongly dependent on its structure. The consequences of these findings on the calculated neutron-capture cross sections are discussed.
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© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
