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Ab initio calculation of the potential bubble nucleus 34Si

Duguet, T, Somà, V, Lecluse, S, Barbieri, Carlo and Navrátil, P (2017) Ab initio calculation of the potential bubble nucleus 34Si Physical Review C: Nuclear Physics, 95, 034319.

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Background: The possibility that an unconventional depletion (referred to as a “bubble”) occurs in the center of the charge density distribution of certain nuclei due to a purely quantum mechanical effect has attracted theoretical and experimental attention in recent years. Based on a mean-field rationale, a correlation between the occurrence of such a semibubble and an anomalously weak splitting between low angular-momentum spin-orbit partners has been further conjectured. Energy density functional and valence-space shell model calculations have been performed to identify and characterize the best candidates, among which 34 Si appears as a particularly interesting case. While the experimental determination of the charge density distribution of the unstable 34 Si is currently out of reach, ( d , p ) experiments on this nucleus have been performed recently to test the correlation between the presence of a bubble and an anomalously weak 1 / 2 − − 3 / 2 − splitting in the spectrum of 35 Si as compared to 37 S .Purpose: We study the potential bubble structure of 34 Si on the basis of the state-of-the-art ab initio self-consistent Green's function many-body method. Methods: We perform the first ab initio calculations of 34 Si and 36 S . In addition to binding energies, the first observables of interest are the charge density distribution and the charge root-mean-square radius for which experimental data exist in 36 S . The next observable of interest is the low-lying spectroscopy of 35 Si and 37 S obtained from ( d , p ) experiments along with the spectroscopy of 33 Al and 35 P obtained from knock-out experiments. The interpretation in terms of the evolution of the underlying shell structure is also provided. The study is repeated using several chiral effective field theory Hamiltonians as a way to test the robustness of the results with respect to input internucleon interactions. The convergence of the results with respect to the truncation of the many-body expansion, i.e., with respect to the many-body correlations included in the calculation, is studied in detail. We eventually compare our predictions to state-of-the-art multireference energy density functional and shell model calculations. Results: The prediction regarding the (non)existence of the bubble structure in 34 Si varies significantly with the nuclear Hamiltonian used. However, demanding that the experimental charge density distribution and the root-mean-square radius of 36 S be well reproduced, along with 34 Si and 36 S binding energies, only leaves the NNLO sat Hamiltonian as a serious candidate to perform this prediction. In this context, a bubble structure, whose fingerprint should be visible in an electron scattering experiment of 34 Si , is predicted. Furthermore, a clear correlation is established between the occurrence of the bubble structure and the weakening of the 1 / 2 − − 3 / 2 − splitting in the spectrum of 35 Si as compared to 37 S .Conclusions: The occurrence of a bubble structure in the charge distribution of 34 Si is convincingly established on the basis of state-of-the-art ab initio calculations. This prediction will have to be reexamined in the future when improved chiral nuclear Hamiltonians are constructed. On the experimental side, present results act as a strong motivation to measure the charge density distribution of 34 Si in future electron scattering experiments on unstable nuclei. In the meantime, it is of interest to perform one-neutron removal on 34 Si and 36 S in order to further test our theoretical spectral strength distributions over a wide energy range.

Item Type: Article
Subjects : Physics
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
Duguet, T
Somà, V
Lecluse, S
Navrátil, P
Date : 24 March 2017
DOI : 10.1103/PhysRevC.95.034319
Copyright Disclaimer : ©2017 American Physical Society
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 26 Apr 2017 15:26
Last Modified : 16 Jan 2019 17:14

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