Implications of occupancy of 2s1/2 state in sd-shell within RMF+BCS approach

Abstract

We employ the relativistic mean-field plus BCS (RMF+BCS) approach to study the behavior of [Formula: see text]-shell by investigating in detail the single particle energies, and proton and neutron density profiles along with the deformations and radii of even–even nuclei. Emergence of new shell closure, weakly bound structure and most recent phenomenon of bubble structure are reported in the [Formula: see text]-shell. [Formula: see text]C, [Formula: see text]O and [Formula: see text]S are found to have a weakly bound structure due to particle occupancy in 2[Formula: see text] state. On the other hand [Formula: see text]O, [Formula: see text]Ca and [Formula: see text]Si are found with depleted central density due to the unoccupied 2[Formula: see text] state and hence they are the potential candidates of bubble structure. [Formula: see text]C and [Formula: see text]O emerge as doubly magic with [Formula: see text] in accord with the recent experiments and [Formula: see text]S emerges as a new proton magic nucleus with [Formula: see text]. [Formula: see text] and [Formula: see text] are predicted as magic numbers in doubly magic [Formula: see text]O, [Formula: see text]Ca and [Formula: see text]Si, respectively. These results are found in agreement with the recent experiments and have consistent with the other parameters of RMF and other theories.

Bubble nuclei within the self-consistent Hartree-Fock mean field plus pairing approach

“…These experiments confirmed the theoretical predictions [20] that the single-particle strength of the proton-hole configuration 3s 1/2 in 205 Tl amounts to 70%-90%, whereas the remaining strength of 30%-10% is mainly exhausted in the two-neutron hole configuration 2d 3/2 [18]. This indicates that the candidates to the bubble structure must have unoccupied s levels, such as 22 O and 34 Si (unoccupied 2s level) [9,11], 46 Ar (unoccupied 2s level) [8,21], and 206 Hg (unoccupied 3s level) [21]. In these bubble candidates, the shell closure often takes place when the states of low angular momenta are located at or near the top of the Fermi energy.…”

“…Hence the depletion of the spin-orbit splitting around the nuclear center can be explained by the bubble structure [10,25]. The results obtained at T = 0 within the present work are also compared with the predictions by the Hartree-Fock-Bogolyubov (HFB) approach [9,11,29].…”

“…The 2s 1/2 level is the lowest unoccupied level above the Fermi one, whose occupancy was recently measured at T = 0 to be 0.17 ± 0.03 [24]. This very low occupancy of the was predicted to have the neutron bubble structure at T = 0 [9,11]. Hence, the calculation is also carried out for seven selected neutron shells similar to those in 34 Si.…”

“…Siemens and Bethe also discussed the existence of stable spherical shells [2]. The first microscopic model of the bubble structure was presented by Campi and Sprung in 1973 [3], initiating many works by other authors ever since [4][5][6][7][8][9][10][11]. In recent years, the study of the nuclear bubble structure was extended to superheavy and hyperheavy nuclei [12][13][14][15][16][17].…”

Evolution of Shapes and Search for Shape Coexistence in Sd-Shell Nuclei

“…Various theoretical models have been showing keen interest in searching the shape coexistence in many isotopic as well as isotonic chains. In this paper, we employ Relativistic Mean-Field plus BCS (RMF+BCS) approach [6,7] to investigate the shape coexistence and transition in light mass nuclei between Z = 10 -16 with NL3* force parameter [8]. To fortify our results of shape evolution we will compare our results with our another calculation using Macroscopic-microscopic approach (Mac-Mic) with Nilson Strutinsky (NS) prescription [9,10] which also includes triaxial deformation and with the results of Lalazissis et al [11].…”