Ab initio calculation of the potential bubble nucleus ~(34)Si

摘要

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 expans