M. Bhuyan

Superdeformed and hyperdeformed states in Z = 122 isotopes

Department of Physics, Panjab University, Chandigarh-160014, India.(Dated: May 30, 2009)We calculate the binding energy, root-mean-square radius and quadrupole deformation parameter for the re-cent, possibly discovered superheavey element Z=122, using the axially deformed relativistic mean field (RMF)and non-relativistic Skyrme Hartree-Fock (SHF) formalisms. The calculation is extended to include various iso-topes of Z=122 element, strarting from A=282 to A=320. We predict highly deformed structures in the groundstate for all the isotopes. A shape transition appears at about A=290 from a highly oblate to a large prolate shape,which may be considered as the superdeformed and hyperdeformed structures of Z=122 nucleus in the meanfield approaches. The most stable isotope (largest binding e nergy per nucleon) is found to be

MAGIC NUCLEI IN SUPERHEAVY VALLEY

An extensive theoretical search for the proton magic number in the superheavy valley beyond Z = 82 and the corresponding neutron magic number after N = 126 is carried out. For this we scanned a wide range of elements Z = 112–130 and their isotopes. The well-established non-relativistic Skryme–Hartree–Fock and Relativistic Mean Field formalisms with various force parameters are used. Based on the calculated systematics of pairing gap, two-neutron separation energy and the shell correction energy for these nuclei, we find Z = 120 as the next proton magic and N = 172, 182/184, 208 and 258 the subsequent neutron magic numbers.

Effect of isospin asymmetry in a nuclear system

The effect of δ- and ω–ρ-meson cross couplings on asymmetry nuclear systems is analyzed in the framework of an effective field theory motivated relativistic mean field formalism. The calculations are done on top of the G2 parameter set, where these contributions are absent. We calculate the root mean square radius, binding energy, single particle energy (for the first and last occupied orbits), density and spin–orbit interaction potential for some selected nuclei and evaluate the Lsym- and Esym-coefficients for nuclear matter as a function of δ- and ω–ρ-meson coupling strengths. As expected, the influence of these effects is negligible for the symmetry nuclear system and these effects are very important for systems with large isospin asymmetry.

NUCLEAR SUB-STRUCTURE IN 112–122Ba NUCLEI WITHIN RELATIVISTIC MEAN FIELD THEORY

Working within the framework of relativistic mean field theory, we study for the first time the clustering structure (nuclear sub-structure) of 112–122Ba nuclei in an axially deformed cylindrical coordinate. We calculate the individual neutrons and protons density distributions for Ba-isotopes. From the analysis of the clustering configurations in total (neutrons-plus-protons) density distributions for various shapes of both the ground and excited states, we find different sub-structures inside the Ba nuclei considered here. The important step, carried out here for the first time, is the counting of number of protons and neutrons present in the clustering region(s). 12C is shown to constitute the cluster configuration in prolate-deformed ground-states of 112–116Ba and oblate-deformed first excited states of 118–122Ba nuclei. Presence of other lighter clusters such as 2H, 3H and nuclei in the neighborhood of N = Z, 14N, 34–36Cl, 36Ar and 42Ca are also indicated in the ground and excited states of these nuclei. Cases with no cluster configuration are shown for 112–116Ba in their first and second excited states. All these results are of interest for the observed intermediate-mass-fragments and fusion–fission processes, and the so far unobserved evaporation residues from the decaying Ba* compound nuclei formed in heavy ion reactions.

Λ-hyperon interaction with nucleons

We study the interaction of Λ-hyperon with proton and neutron inside a nucleus within the framework of relativistic mean field (RMF) formalism. The single-particle energy levels for some of the specific proton and neutron orbits are analyzed with the addition of Λ-successively. The neutron energy level is more deeper, because of decrease in symmetry energy due to substitution of neutron by Λ-hyperon.

THE α-DECAY CHAINS OF THE 287, 288115 ISOTOPES USING RELATIVISTIC MEAN FIELD THEORY

We study the binding energy, root-mean-square radius and quadrupole deformation parameter for the synthesized superheavy element Z = 115, within the formalism of relativistic mean field theory. The calculation is dones for various isotopes of Z = 115 element, starting from A = 272 to A = 292. A systematic comparison between the binding energies and experimental data is made.The calculated binding energies are in good agreement with experimental result. The results show the prolate deformation for the ground state of these nuclei. The most stable isotope is found to be 282115 nucleus (N = 167) in the isotopic chain. We have also studied Qα and Tα for the α-decay chains of 287, 288115.

Application of relativistic mean field and effective field theory densities to scattering observables for Ca isotopes

In the framework of relativistic mean field (RMF) theory, we have calculated the density distribution of protons and neutrons for {sup 40,42,44,48}Ca with NL3 and G2 parameter sets. The microscopic proton-nucleus optical potentials for p+{sup 40,42,44,48}Ca systems are evaluated from the Dirac nucleon-nucleon scattering amplitude and the density of the target nucleus using relativistic-Love-Franey and McNeil-Ray-Wallace parametrizations. We have estimated the scattering observables, such as the elastic differential scattering cross section, analyzing power and the spin observables with the relativistic impulse approximation (RIA). The results have been compared with the experimental data for a few selective cases and we find that the use of density as well as the scattering matrix parametrizations are crucial for the theoretical prediction.

The evaporation residue in the fission state of barium nuclei within relativistic mean-field theory

The evaporation residue of barium isotopes is investigated in a microscopic study using relativistic mean field theory. The investigation includes the isotopes of barium from the valley of stability to the exotic proton-rich region. The ground as well as neck configurations for these nuclei are generated from their total nucleonic density distributions of the corresponding state. We have estimated the constituents (number of nucleons) in the elongated neck region of the fission state. We found the α-particle as the constituent of the neck of Ba-isotopes, referred to as the evaporated residue in heavy-ion reaction studies. A strong correlation between the neutron and proton is observed throughout the isotopic chain.

The structural and decay properties of Francium isotopes

We study the bulk properties such as binding energy (BE), root-mean-square (RMS) charge radius, quadrupole deformation etc. for Francium (Fr) isotopes having mass number A = 180–240 within the framework of relativistic mean field (RMF) theory. Systematic comparisons are made between the calculated results from RMF theory, Finite Range Droplet Model (FRDM) and the experimental data. Most of the nuclei in the isotopic chain shows prolate configuration in their ground state. The α-decay properties like α-decay energy and the decay half-life are also estimated for three different chains of 198Fr, 199Fr and 200Fr. The calculation for the decay half-life are carried out by taking two different empirical formulae and the results are compared with the experimental data.

Search of double shell closure in the superheavy nuclei using a simple effective interaction

This paper refers to another attempt to search for spherical double shell closure nuclei beyond Z = 82, N = 126. All calculations and results are based on a newly developed approach entitled as simple effective interaction (SEI). Our results predict that the combination of magic nucleus occurs at N = 182 (Z = 114, 120, 126). All possible evidences for the occurrence of magic nuclei are discussed systematically. And, the obtained results for all observables are compared with the relativistic mean field theory for NL3 parameter.