Systematics of the low-energy electric dipole strength in the Sn isotopic chain
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arXiv
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| Format: | Preprint |
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2023
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| author | Markova, M. von Neumann-Cosel, P. Litvinova, E. |
| author_facet | Markova, M. von Neumann-Cosel, P. Litvinova, E. |
| contents | We present a systematic study of the mass dependence of the low-energy electric dipole strength (LEDS) in Sn isotopes in the range $ A = 111 - 124$ based on data obtained with the Oslo method and with relativistic Coulomb excitation in forward-angle ($p,p^\prime$) scattering. The combined data cover an energy range of $2 - 20$ MeV which permits, with minimal assumptions, a decomposition of the total strength into the contribution from the low-energy tail of the isovector giant dipole resonance (IVGDR) and possible resonance-like structures on top of it. In all cases, a resonance peaked at about 8.3 MeV is observed, exhausting an approximately constant fraction of the Thomas-Reiche-Kuhn (TRK) sum rule with a local maximum at $^{120}$Sn which might be related to shell structure effects. For heavier isotopes ($A \geq 118$) a consistent description of the data requires the inclusion of a second resonance centered at 6.5 MeV, representing the isovector response of the pygmy dipole resonance (PDR). Its strength corresponds to a small fraction of the total LEDS only and shows an approximately linear dependence on mass number. The experimental results are also compared to ab initio-based microscopic calculations to investigate the importance of an inclusion of quasiparticle vibration coupling (qPVC) for a realistic description of the LEDS. A possible interpretation of the experimentally observed two-bump structure is given. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2311_14525 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Systematics of the low-energy electric dipole strength in the Sn isotopic chain Markova, M. von Neumann-Cosel, P. Litvinova, E. Nuclear Experiment Nuclear Theory We present a systematic study of the mass dependence of the low-energy electric dipole strength (LEDS) in Sn isotopes in the range $ A = 111 - 124$ based on data obtained with the Oslo method and with relativistic Coulomb excitation in forward-angle ($p,p^\prime$) scattering. The combined data cover an energy range of $2 - 20$ MeV which permits, with minimal assumptions, a decomposition of the total strength into the contribution from the low-energy tail of the isovector giant dipole resonance (IVGDR) and possible resonance-like structures on top of it. In all cases, a resonance peaked at about 8.3 MeV is observed, exhausting an approximately constant fraction of the Thomas-Reiche-Kuhn (TRK) sum rule with a local maximum at $^{120}$Sn which might be related to shell structure effects. For heavier isotopes ($A \geq 118$) a consistent description of the data requires the inclusion of a second resonance centered at 6.5 MeV, representing the isovector response of the pygmy dipole resonance (PDR). Its strength corresponds to a small fraction of the total LEDS only and shows an approximately linear dependence on mass number. The experimental results are also compared to ab initio-based microscopic calculations to investigate the importance of an inclusion of quasiparticle vibration coupling (qPVC) for a realistic description of the LEDS. A possible interpretation of the experimentally observed two-bump structure is given. |
| title | Systematics of the low-energy electric dipole strength in the Sn isotopic chain |
| topic | Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2311.14525 |