Approaching the pygmy dipole resonance in Sn isotopes with the Oslo method
Abstract
Collective resonance phenomena in atomic nuclei are historically one of the first and most plentiful sources of unique information on the intricate nuclear structure and properties of nuclear matter. One of them, the pygmy dipole resonance, is commonly recognised as a potential key to the description of dense neutron-rich matter, thus bridging the gap between heavy, neutron-rich nuclei and massive astrophysical objects, such as neutron stars. In this regard, systematic experimental studies of the pygmy dipole resonance are highly desired to guide future improvements in the theoretical description of its underlying mechanisms. This dissertation sheds new light on the evolution of the low-lying electric dipole strength, commonly interpreted as the pygmy dipole resonance, based on a systematic analysis of particle-γ coincidence data from the Oslo Cyclotron Laboratory for eleven Sn isotopes using the Oslo method. Through the investigation of their statistical characteristics, such as nuclear level densities and γ-ray strength functions, the properties of the potential pygmy dipole resonance in Sn nuclei and its impact on the production of heavy elements in the astrophysical intermediate neutron-capture process have been investigated.List of papers
Paper I. Comprehensive Test of the Brink-Axel Hypothesis in the Energy Region of the Pygmy Dipole Resonance. Published in: Physical Review Letters, 127, 182501 (2021). DOI: 10.1103/PhysRevLett.127.182501. (Supplemental Material DOI: 10.1103/PhysRevLett.127.182501). The paper is included in the thesis. Also available at: https://doi.org/10.1103/PhysRevLett.127.182501 |
Paper II. Markova, Maria; Larsen, Ann-Cecilie; von Neumann-Cosel, Peter et al. Nuclear level densities and γ-ray strength functions in 120,124Sn isotopes: Impact of Porter-Thomas fluctuations. Published in: Physical Review C, 106, 034322 (2022). DOI: 10.1103/PhysRevC.106.034322 (Erratum DOI: 10.1103/PhysRevC.109.019901). The paper is included in the thesis. Also available at: https://doi.org/10.1103/PhysRevC.106.034322 |
Paper III. Markova, Maria; Larsen, Ann-Cecilie; Tveten, Gry Merete et al. Nuclear level densities and γ-ray strength functions of 111,112,113Sn isotopes studied with the Oslo method. Published in: Physical Review C, 108, 014315 (2023). DOI: 10.1103/PhysRevC.108.014315. The paper is included in the thesis. Also available at: https://doi.org/10.1103/PhysRevC.108.014315 |
Paper IV. Markova, Maria; Larsen, Ann-Cecilie; von Neumann-Cosel, Peter et al. Systematic study of the low-lying electric dipole strength in Sn isotopes and its astrophysical implications. Published in: Physical Review C, 109, 054311 – Published 8 May 2024. DOI: 10.1103/PhysRevC.109.054311. The paper is included in the thesis. Also available at: https://doi.org/10.1103/PhysRevC.109.054311 |
Paper V. Markova, Marie; von Neumann-Cosel, Peter; Litvinova, Elena. Systematics of the low-energy electric dipole strength in the Sn isotopic chain. To be published. The paper is not available in DUO awaiting publishing. Preprint available at arXiv:2311.14525 |