Global trends of the electric dipole polarizability from shell-model calculations

Orce, José Nicolás; Ngwetsheni, Cebo; Brown, B. Alex

doi:10.1103/physrevc.108.044309

Cited by 3 publications

(4 citation statements)

References 105 publications

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“…particle-hole states originating from cross-shell excitations that give rise to intruder states. In essence, both Hamiltonians are the same near 16 O, with the WBP interaction presenting-as for ground states [52]-slightly smaller polarizability values in the middle and end of the sd shell.…”

Section: Shell-model Calculationsmentioning

confidence: 96%

“…For ground states, α E1 can be deduced using non-degenerate perturbation theory by means of the energy-shift of nuclear levels arising from the quadratic Stark effect [46], and has been investigated with SM calculations [47][48][49][50][51][52] using,…”

Section: Motivationmentioning

confidence: 99%

“…Where possible, we perform 1ÿω SM calculations, compare with available data and explore deviations from the hydrodynamic model [59,60,[63][64][65]. Similar SM calculations of the E1 polarizability for ground states have already been published in [52].…”

Section: Motivationmentioning

confidence: 99%

“…The general procedure involves the calculation of all the E1 and E2 matrix elements following equations ( 9) and (12). Similar SM calculations were performed for ground states and are explained in detail in [52]. For self-conjugate nuclei, we calculate E1 matrix elements connecting all the intermediate GDR states with ΔT = 1; for instance, a total of 6770…”

Section: Shell-model Calculationsmentioning

confidence: 99%

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Electric dipole polarizability of low-lying excited states in atomic nuclei

Orce,

Ngwetsheni

2024

J. Phys. G: Nucl. Part. Phys.

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New equations for the electric dipole polarizability αE1 of low-lying excited states in atomic nuclei — and the related (–2) moment of the total photo-absorption cross section, σ–2 — are inferred in terms of electric dipole and quadrupole matrix elements. These equations are valid for arbitrary angular momenta of the initial/ground and final/excited states and have been exploited in fully converged 1h̄ω shell-model calculations of selected p- and sd-shellnuclei that consider configuration mixing; advancing previous knowledge from 17O to 36Ar, where thousands of electric dipole matrix elements are computed from isovector excitations which include the giant dipole resonance region. Our results are in reasonable agreement with previous shell-model calculations and follow — except for 6,7 Li and 17,18 O — Migdal’s global trend provided by the combination of the hydrodynamic model and second-order non-degenerate perturbation theory. Discrepancies in 6,7Li and 17O arise as a result of the presence of α-cluster configurations in odd-mass nuclei, whereas the disagreement in 18O comes from the mixing of intruder states, which is lacking in the shell-model interactions. More advanced ab initio calculations of the dipole polarizability for low-lying excited states covering all the isovector states within the giant dipole resonance region are missing and could be very valuable to benchmark the results presented here and shed further light on how atomic nuclei polarize away from the ground state

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Section: Shell-model Calculationsmentioning

confidence: 96%

Section: Motivationmentioning

confidence: 99%

Section: Motivationmentioning

confidence: 99%

Section: Shell-model Calculationsmentioning

confidence: 99%

See 2 more Smart Citations

Electric dipole polarizability of low-lying excited states in atomic nuclei

Orce,

Ngwetsheni

2024

J. Phys. G: Nucl. Part. Phys.

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Understanding the relationship between electric dipole polarizability and photonuclear (-2) moment in odd-A actinide nuclei

Kemah,

Yakut,

Tabar

et al. 2024

Phys. Scr.

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The nuclear electric dipole (E1) polarizability (α E1) is mainly dominated by the dynamics of the giant dipole resonance (GDR). α E1 is proportional to the (-2) moment of the total photo nuclear cross-section (σ −2). This research investigates the relationship between α E1 and σ −2, along with the effects of the Pygmy Dipole Resonance (PDR) and GDR in odd-mass actinide nuclei. For the first time, α E1 and σ −2 values have been calculated using the Translational and Galilean Invariant Quasiparticle Phonon Nuclear Model (TGI-QPNM) approach for odd-A actinide nuclei. According to TGI-QPNM results, E1 dipole transitions in the GDR region significantly contribute to σ −2 due to the energy weighting factor. Below the neutron separation threshold, the PDR in neutron-rich nuclei shows a contribution of about 5% to σ −2 values. In this region, E1 polarizability can reach values of 20%–25%. The α E1 values indicate the presence of PDR in these nuclei. Additionally, the Adaptive Neuro-Fuzzy Inference System (ANFIS), a new machine learning method, has been performed to analyze the relationship between α E1 and σ −2. The ANFIS results have been compared with those from the TGI-QPNM and experimental data. The TGI-QPNM model achieves an R2 of 0.85–0.95, while the ANFIS model achieves an R2 of 0.99. Moreover, the study suggests that the ANFIS model, consistent with TGI-QPNM results, could be an effective tool for estimating σ −2 in odd-A actinide nuclei.

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Measurement of the Isolated Nuclear Two-Photon Decay in Ge72

Freire-Fernández,

Korten,

Chen

et al. 2024

Phys. Rev. Lett.

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The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the 2γ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to ∼100 keV and half-lives as short as ∼10 ms. The half-life for the 2γ decay of the first-excited 0+ state in bare Ge72 ions was determined to be 23.9(6) ms, which strongly deviates from expectations. Published by the American Physical Society 2024

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Global trends of the electric dipole polarizability from shell-model calculations

Cited by 3 publications

References 105 publications

Electric dipole polarizability of low-lying excited states in atomic nuclei

Electric dipole polarizability of low-lying excited states in atomic nuclei

Understanding the relationship between electric dipole polarizability and photonuclear (-2) moment in odd-A actinide nuclei

Measurement of the Isolated Nuclear Two-Photon Decay in Ge72

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