48Si: An atypical nucleus?

Abstract

Based on the relativistic Hartree-Fock formalism and one of the most advanced Lagrangian PKA1, we investigate the properties of the exotic nucleus 48 Si. We found that 48 Si may be an atypical nucleus characterized by i) the onset of doubly magicity, ii) its location at the drip line, iii) the presence of a doubly semibubble (central depletion of the neutron and proton density profiles) in the ground state, and iv) the occurrence of pairing reentrance at finite temperature. These phenomenons are not independent from each others. We illustrate for instance that the doubly semibubble reduces the spin-orbit splitting of low-orbitals and modifies the splitting of relevant pseudospin partners, favoring N = 34 as a new magic number for neutron rich nuclei. Since 48 Si is predicted doubly magic, it could have an extra stability which puts it at the drip line. Moreover, 48 Si may have interesting excited states which may induce pairing reentrance at finite temperature. While not being new, these phenomenons are found to serendipitously occur together in 48 Si, from our theoretical calculation. Theoretical nuclear modelings are known to be poorly predictive in general, and we asset our confidence in the prediction of our modeling on the fact that the predictions of PKA1 in various regions of the nuclear chart have systematically been found correct and more specifically in the region around 48 Si, our approach correctly reproduce the known features of neighboring nuclei. Whether our predictions are confirmed or not, 48 Si provides a concrete benchmark for the understanding of the nature of nuclear forces.

A systematic study of the factors affecting central depletion in nuclei

“…[21]. The prolately deformed nuclei 40 Mg and 44 S exhibit somewhat larger central depletion in comparison to the oblate nucleus 42 Si. The spread in the values of b p for in 40 Mg, 42 Si and 44 S may be partly due to the variation in the deformation parameter obtained for different models.…”

“…The b p for these nuclei is decreasing on the prolate side even though the occupancy in 2s 1/2 is vanishingly small. The value of b p (highlighted by squares in 5(c)) corresponding to the respective energy minima for 40 Mg, 44 S and 42 Si, are found to be b p = 0.15, 0.16 and 0.08, respectively, even the absolute value of β is almost same for these nuclei. The lower value of b p in 42 Si (oblate) could be due to combined effect of deformation and occupancy of 2s 1/2 state.…”

“…Si[1] and 48 Si[6,40]. Since the pairing correlations are expected Variations of bubble parameter b p , occupancy of 2s 1/2 state, deformation and pairing energy contribution (in MeV) as a function of neutron number for full isotopic chain of Si.…”

Electric dipole polarizability in neutron-rich Sn isotopes as a probe of nuclear isovector properties

“…One way to solve the problem and constrain L stiffly is to find a direct and model-independent correlation between α D and L. Although the previous studies have shown that the model-independent linear correlation only exists between α D J and L, it was only limited to stable nuclei or nuclei near β-stability line. It is well known that exotic phenomena will present when approaching to nuclei far from β-stability line, such as novel shell structures [40][41][42][43][44], new types of excitations [23,45,46], and so on. For E1 excitations, the pygmy dipole resonance (PDR) appears in neutron-rich nuclei [23,45,46], which would cause different characteristics of E1 excitations compared to the ones around β-stability line, and further affect α D .…”

Tensor-force effects on shell-structure evolution in $N = 82$ isotones and $Z = 50$ isotopes in the relativistic Hartree-Fock theory

“…On the other hand, the tensor force is mixed together with the other components, e.g., the spin-orbit force and other central forces. This leads to great difficulties in the quantitative analysis of the tensor force in CDFT, despite the noticeable progress on the tensor-force effects arising from the π-pseudovector and ρ-tensor couplings [26,[58][59][60][61][62]. In particular, a set of formula with Lorentz covariance were developed to describe the spin-dependent nature of the nuclear force within the RHF theory in 2015, and they could reproduce the spin dependence of the two-body interaction matrix elements quite well [63][64][65].…”