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[en] The traditional neutron magic nuclei with N=8, 20, 28, 50 and 126, and those with sub-magic number N = 40 are investigated within the relativistic mean-field plus BCS (RMF+BCS) approach wherein the single particle continuum corresponding to the RMF is replaced by a set of discrete positive energy states for the calculation of pairing energy
[en] Experiments with radioactive nuclear beams provide the opportunity to study very short-lived nuclei with very large isospins. Theoretical descriptions of drip line nuclei in terms of mean field theories, both nonrelativistic as well as relativistic mean fields (RMF), have been well received. Recently it has been shown that the relativistic mean-field (RMF) plus BCS approach wherein the continuum has been replaced by the discrete single particle states for the calculation of the pairing energy provides an alternative fast approach to the relativistic Hartree-Fock-Bogoliubov (RHB) description of the drip-line nuclei. In the analogy of our previous publication on proton magic nuclei, we have employed RMF + BCS approach for the study of neutron magic nuclei with neutron number N = 28 near the drip-line
[en] Production of radioactive beams have facilitated the nuclear structure studies away from the line of β-stability, especially for the neutron rich drip line nuclei. Theoretical investigations of these nuclei have been carried out by using various approaches viz. few body model or clusters, shell model and mean field theories, both nonrelativistic as well as relativistic mean field (RMF). The advantage of the RMF approach, however, is that in this treatment the spin-orbit interaction is included in a natural way. This is especially advantageous for the description of drip-line nuclei for which the spin-orbit interaction plays an important role. In this communication we report briefly the results of our calculations for the Si isotopes carried out within the framework of RMF + BCS approach
[en] Experimental and theoretical studies of exotic nuclei with extreme isospin values present one of the most active areas of research in nuclear physics . Experiments with radioactive nuclear beams provide the opportunity to study very short-lived nuclei with very large neutron to proton ratios N/Z. Recent experiments with radioactive nuclear beams (RNB) have provided, apart from many other interesting results, strong indications for the disappearance of traditional magic numbers as well as appearance of new magic numbers in nuclei with exotic isospin values
[en] The theoretical study of halo nuclei may be broadly categorized into two groups. The first category includes the descriptions envisaging a cluster like structure of halo nucleus which is composed of a core plus one, two or even several neutrons loosely bound to core. In the second category one has the shell model and the mean-field theoretic frameworks, especially the relativistic mean-field (RMF) approach which have been successfully employed
[en] In the present investigations we have employed relativistic mean-field plus BCS (RMF + BCS) approach to study the variation of root mean square radii and the density profiles for the entire chain of even even N = 28 isotones upto drip-lines. Root mean square radii for the nuclei of the N = 28 isotonic chain obtained from our deformed RMF + BCS calculations and spherical RMF + BCS calculations with TMA force parameters have been displayed along with the available experimental data for the purpose of comparison. It is observed that with increasing number of protons the rms radius for the proton distribution rp increases gradually to have maximum value for the heaviest bound nucleus 3058Zn28 for N = 28 isotonic chain. A comparison shows that the deformed RMF results for the nuclei with Z = 12, 14 and 16 are not similar to those obtained from the spherical RMF calculations as the nuclei with Z = 12, 14 and 16 are appreciably deformed
[en] A systematic study of the ground-state properties of the entire chains of even–even neutron magic nuclei represented by isotones of traditional neutron magic numbers N = 8, 20, 40, 50, 82, and 126 has been carried out using relativistic mean-field plus Bardeen–Cooper–Schrieffer approach. Our present investigation includes deformation, binding energy, two-proton separation energy, single-particle energy, rms radii along with proton and neutron density profiles, etc. Several of these results are compared with the results calculated using nonrelativistic approach (Skyrme–Hartree–Fock method) along with available experimental data and indeed they are found with excellent agreement. In addition, the possible locations of the proton and neutron drip-lines, the (Z, N) values for the new shell closures, disappearance of traditional shell closures as suggested by the detailed analyzes of results are also discussed in detail.
[en] Inspired by the recent experiments indicating doubly magic nuclei that lie near the drip-line and encouraged by the success of our relativistic mean-field (RMF) plus state-dependent BCS approach to the description of the ground-state properties of drip-line nuclei, we develop this approach further, across the entire periodic table, to explore magic nuclei, loosely bound structures, and halo formation in exotic nuclei. In our RMF+BCS approach, the single-particle continuum corresponding to the RMF is replaced by a set of discrete positive-energy states for the calculations of pairing energy. Detailed analysis of the single-particle spectrum, pairing energies, and densities of the nuclei predict the unusual proton shell closures at proton numbers Z = 6, 14, 16, 34, and unusual neutron shell closures at neutron numbers N = 6, 14, 16, 34, 40, 70, 112. Further, in several nuclei like the neutron-rich isotopes of Ca, Zr, Mo, etc., the gradual filling of lowlying single-particle resonant state together with weakly bound single-particle states lying close to the continuum threshold helps accommodate more neutrons but with an extremely small increase in the binding energy. This gives rise to the occurrence of loosely bound systems of neutron-rich nuclei with a large neutron-to-proton ratio. In general, the halo-like formation, irrespective of the existence of any resonant state, is seen to be due to the large spatial extension of the wave functions for the weakly bound single-particle states with low orbital angular momentum having very small or no centrifugal barriers.