Narrow Results

The systematic investigation of shape evolution between spherical U(5) and γ-unstable O(6) for Mo isotopes has been carried out by the microscopic quadrupole constrained relativistic mean field model plus BCS method with all the most used interactions, i.e. PK1, NL3, TM1 and NLSH. The calculated potential energy surfaces show a clear shape evolution for the even–even Mo isotopes with N = 50~64 and ⁹⁴Mo is suggested to be the γ-unstable nucleus, which is favored by the experimental data. Similar conclusion is also drawn from the neutron single particle spectra.

Constrained Hartree–Fock–Bogoliubov theory with SLy4 and SLy5 Skyrme forces is used to investigate the shape transition between spherical and γ-unstable nuclei in ^38–66Ti. By examining potential energy curves and neutron single-particle levels of even–even Ti isotopes, ^46,52,60Ti are suggested as possible candidates of the nuclei with E(5) symmetry.

The nuclear potential energies of neutron deficient even–even rare earth nuclei ¹⁵⁸Er and ¹⁶²Hf for the spin range 0–60 are computed within the framework of cranked Nilsson–Strutinsky shell correction method. The potential energy surface diagrams are analyzed in terms of quadrupole deformation and triaxiality parameter. The shape evolution of these isotopes with respect to spin is studied. The spin dependence of nuclear equilibrium potential energy is also verified.

The shapes and low-energy spectra of ${}^{176-194}$Pt isotopes are discussed by a nonrelativistic Skyrme–Hartree–Fock (SHF) approach plus a density-dependent pairing in the BCS approximation. Two different Skyrme parameters SLy5 and SGII are used to perform constrained triaxial mean-field calculations of energy surface. The calculations beyond mean field are introduced by a projection of mean-field intrinsic wave functions onto good angular momentum. Theoretical calculations exhibit the evolution of shapes from triaxial in light Pt isotopes to $\gamma$ soft for medium Pt isotopes, and finally oblate shapes in heavy isotopes. In particular, the calculated excitation spectra are in good agreement with available data and the trend of experimental $B(E2)$ is reproduced. The mean-field calculations indicate a stable shape evolution with SLy5 and SGII interactions, respectively. In the present SHF approach, the lighter nuclei Pt isotopes present a slightly triaxial shapes.

The nuclear potential energies of Lu isotopes with neutron number $N=90-98$ up to high spins are computed within the framework of the unpaired cranked Nilsson–Strutinsky method. The potential and the macroscopic Lublin–Strasbourg drop (LSD) energy-surface diagrams are analyzed in terms of quadrupole deformation and triaxiality parameter. The shape evolution of these isotopes with respect to angular momentum, as well as the neutron number is studied.

In this work, the ground state properties of the platinum isotopic chain, ${}^{160-238}$Pt are studied within the covariant density functional theory. The calculations are carried out for a large number of even–even Pt isotopes by using the density-dependent point-coupling and the density-dependent meson-exchange effective interactions. All ground state properties such as the binding energy, separation energy, two-neutron shell gap, root mean square (rms)-radii for neutrons and protons and quadrupole deformation are discussed and compared with available experimental data, and with the predictions of some nuclear models such as the Relativistic Mean Field (RMF) model with NL3 functional and the Hartree–Fock–Bogoliubov (HFB) method with SLy4 Skyrme force. The shape phase transition for Pt isotopic chain is also studied. Its corresponding total energy curves as well as the potential energy surfaces confirm the transition from prolate to oblate shapes at ${}^{188}$Pt contrary to some studies predictions and in agreement with others. Overall, a good agreement is found between the calculated and experimental results wherever available.

We study the effect of ZnO source and growth temperatures on morphology of the ZnO nanostructures. Nanostructures grown from ZnO nanopowder show the shape evolution from nanowires to nanoribbons and then to nanorods with variation in growth temperature and zinc vapor pressure. At 750°C, only vertically aligned nanowires have been observed and with increase in growth temperature nanowires transforms to nanoribbons and then finally to nanorods at 870°C. On the other hand, in case of ZnO bulk powder as a source material, only nanowires are produced at all temperatures. Raman scattering studies on the nanostructures show distinct mode at ~ 437 cm^-1, confirming the hexagonal wurtzite phase of the as grown nanostructures. Room temperature photoluminescence spectra exhibit bound exciton related strong UV emission at ~ 379 nm indicating high quality of the as-grown nanostructures. Possible mechanism of growth and shape evolution in ZnO nanostructures are explored through systematic studies of the effect of growth temperatures and zinc vapor pressure.

The structure of low-lying excitation states of even-even N = 40 isotones is studied using a five-dimensional collective Hamiltonian with the collective parameters determined from the relativistic mean-field plus BCS method with the PC-PK1 functional in the particle-hole channel and a separable paring force in the particle-particle channel. The theoretical calculations in mean-field level present a picture of spherical-oblate-prolate shape transition in the N = 40 isotones and the systematics of the low-lying states along the isotonic chain is reproduced.

It was recently found that remarkably accurate fission-fragment mass distributions can be obtained by treating the nuclear shape evolution as a Metropolis walk on previously calculated five-dimensional potential-energy surfaces; this novel method is briefly reviewed here.