We employed the Skyrme-Hartree-Fock model to investigate the density distributions and their dependence on nuclear shapes and isospins in the superheavy mass region. Different Skyrme forces were used for the calculations with a special comparison to the experimental data in 208Pb. The ground-state deformations, nuclear radii, neutron-skin thicknesses and ±-decay energies were also calculated. Density distributions were discussed with the calculations of single-particle wave functions and shell fillings. Calculations show that deformations have considerable effects on the density distributions, with a detailed discussion on the 292120 nucleus. Earlier predictions of remarkably low central density are not supported when deformation is allowed for. © 2005 The American Physical Society.

A method of calculating giant resonance strength functions using Time-Dependent Hartree-Fock techniques is described. An application to isoscalar giant monopole resonances in spherical nuclei is made, thus allowing a comparison between independent 1-, 2- and 3-Dimensional computer codes.

We employed the Skyrme-Hartree-Fock + BCS model to investigate the density distributions of even-even superheavy nuclei around the predicted magic numbers of Z d 114, 120, 126 and N d 172, 184. The central depressions in densities are shown in the heaviest nuclei with Z d 120 and N d 178, which is due to high-j orbits occupied. However, densities become flatter when deformations occur. The superheavy nuclei with N d 180-188 and Z d 126 have no central depressions, due to that low-j orbits become occupied. Shell closures in the superheavy mass region are isospin dependent. © 2005 IOP Publishing Ltd.

A Java implementation of a suite of programs was described to calculate the angular momentum coupling coefficients analytically. The angular momentum coupling coefficients were found in problems involving quantum mechanical theory of angular momentum. The operating systems under which the program was tested included Netscape 4.75 on Solaris 7 and Internet Explorer 5.5 on Windows NT4.

The nuclear mean-field model based on Skyrme forces or related density functionals has found widespread application to the description of nuclear ground states, collective vibrational excitations, and heavy-ion collisions. The code Sky3D solves the static or dynamic equations on a three-dimensional Cartesian mesh with isolated or periodic boundary conditions and no further symmetry assumptions. Pairing can be included in the BCS approximation for the static case. The code is implemented with a view to allow easy modifications for including additional physics or special analysis of the results.

The half-life of the yrast I À = 2+ state in the neutron-rich nucleus 188W has been measured using fast-timing
techniques with the HPGe and LaBr3:Ce array at the National Institute of Physics and Nuclear Engineering,
Bucharest. The resulting value of t1/2 = 0.87(12) ns is equivalent to a reduced transition probability of
B(E2; 2+
1 ’ 0+
1 ) = 85(12) W.u. for this transition. The B(E2; 2+
1 ’ 0+
1 ) is compared to neighboring tungsten
isotopes and nuclei in the Hf, Os, and Pt isotopic chains. Woods-Saxon potential energy surface (PES) calculations
have been performed for nuclei in the tungsten isotopic chain and predict prolate deformed minima with rapidly
increasing ³ softness for 184?192W and an oblate minimum for 194W.

Background: The study of the nuclear equation of state (EOS) and the behavior of nuclear matter under extreme conditions is crucial to our understanding of many nuclear and astrophysical phenomena. Nuclear reactions serve as one of the means for studying the EOS. Purpose: It is the aim of this paper to discuss the impact of nuclear fusion on the EOS. This is a timely subject given the expected availability of increasingly exotic beams at rare isotope facilities [A. B. Balantekin et al., Mod. Phys. Lett. A 29, 1430010 (2014)]. In practice, we focus on 48Ca+48Ca fusion. Method: We employ three different approaches to calculate fusion cross sections for a set of energy density functionals with systematically varying nuclear matter properties. Fusion calculations are performed using frozen densities, using a dynamic microscopic method based on density-constrained time-dependent Hartree-Fock (DC-TDHF) approach, as well as direct TDHF study of above barrier cross sections. For these studies, we employ a family of Skyrme parametrizations with systematically varied nuclear matter properties. Results: The folding-potential model provides a reasonable ?rst estimate of cross sections. DC-TDHF, which includes dynamical polarization, reduces the fusion barriers and delivers much better cross sections. Full TDHF near the barrier agrees nicely with DC-TDHF. Most of the Skyrme forces which we used deliver, on the average, fusion cross sections in good agreement with the data. Trying to read off a trend in the results, we ?nd a slight preferenceforforceswhichdeliveraslopeofsymmetryenergyofL H 50MeVthatcorrespondstoaneutron-skin thickness of 48Ca of Rskin = (0.180?0.210) fm. Conclusions: Fusion reactions in the barrier and sub-barrier region can be a tool to study the EOS and the neutron skin of nuclei. The success of the approach will depend on reduced experimental uncertainties of fusion data as well as the development of fusion theories that closely couple to the microscopic structure and dynamics.

Background: It is generally acknowledged that the time-dependent Hartree-Fock (TDHF) method provides a useful foundation for a fully microscopic many-body theory of low-energy heavy-ion reactions. The TDHF method is also known in nuclear physics in the small amplitude domain, where it provides a useful description of collective states, and is based on the mean-?eld formalism which has been a relatively successful approximation to the nuclear many-body problem. Currently, the TDHF theory is being widely used in the study of fusion excitation functions, ?ssion, deep-inelastic scattering of heavy mass systems, while providing a natural foundation for many other studies. Purpose: With the advancement of computational power it is now possible to undertake TDHF calculations without any symmetry assumptions and incorporate the major strides made by the nuclear structure community in improving the energy density functionals used in these calculations. In particular, time-odd and tensor terms in these functionals are naturally present during the dynamical evolution, while being absent or minimally important for most static calculations. The parameters of these terms are determined by the requirement of Galilean invariance or local gauge invariance but their signi?cance for the reaction dynamics have not been fully studied. This work addresses this question with emphasis on the tensor force. Method: The full version of the Skyrme force, including terms arising only from the Skyrme tensor force, is applied to the study of collisions within a completely symmetry-unrestricted TDHF implementation. Results: We examine the e?ect on upper fusion thresholds with and without the tensor force terms and ?nd an e?ect on the fusion threshold energy of the order several MeV. Details of the distribution of the energy within terms in the energy density functional is also discussed. Conclusions: Terms in the energy density functional linked to the tensor force can play a non-negligible role in dynamic processes in nuclei.

My research has been focused on time-dependent aspects of nuclear physics both at the mean-field and at the beyond-mean-field level. At the mean field level, the objective of my PhD has been to understand how the introduction of the tensor part of the Skyrme interaction affects heavy ion collisions and giant magnetic resonances, in a self consistent and symmetry unrestricted manner. The introduction of the tensor force redistributes the strength of the giant magnetic resonances within the same energy range. Within the study of heavy ion collisions of 16O+16O the introduction of the tensor decreased the amount of dissipation in the system. At the beyond mean field level, the objective of my PhD was to implement a time dependent density matrix (TDDM) theory, self consistently, without symmetry restrictions using the full Skyrme force. TDDM allows an order by order truncation of the Bogoliubov-Born-ýýGreen-ýýKirkwood-ýýYvon (BBGKY) hierarchy, which relates the evolution of many body densities. If two-body correlations are assumed to dominate the dynamics of the system, the resulting equations incorporate one-particle-one-hole and two-particle-two-hole correlations. A variety of different nuclei below A=40 were chosen to study the formation of correlations for different nuclear ground states. Two body correlations were found to have a noticeable effect on the ground state properties of these nuclei. For example on average 4 - 5 % of the total energy is due to correlations. When time dependent calculations were performed with these correlated nuclei, computational limitations led to problems with conservation laws.

The nuclear mean-field model based on Skyrme forces or related density functionals has found widespread application to the description of nuclear ground states, collective vibrational excitations, and heavy-ion collisions. The code Sky3D solves the static or dynamic equations on a three-dimensional Cartesian mesh with isolated or periodic boundary conditions and no further symmetry assumptions. Pairing can be included in the BCS approximation for the static case. The code is implemented with a view to allow easy modifications for including additional physics or special analysis of the results.

The mass distributions for giant dipole resonances in S-32 and Sn-132 decaying through particle emission and for deep-inelastic collisions between O-16 nuclei have been investigated by implementing the Balian-Vénéroni variational technique based upon a three-dimensional time-dependent Hartree-Fock code with realistic Skyrme interactions. The mass distributions obtained have been sown to be significantly larger than standard TDHF results.

Recent experimental data on the low-lying states in W-190 show a change in the E(4(1)(+))/E(2(1)(+)) behavior compared to less neutron-rich neigbors. Self-consistent axially-deformed Hartree-Fock calculations, using a separable monopole interaction, of nuclei in the vicinity of W-190 are performed to systematically examine the evolution of ground state quadrupole deformations. It is found that the neutron number N=116 causes a coexistence of oblate and prolate shapes, with a weak dependence on proton number, thereby hindering the development of these isotones as well-deformed rotors.

A previously unreported isomer has been identified in Mo-99 at an excitation energy of E-x = 3010 keV, decaying with a half-life of T-1/2 = 8(2) ns. The nucleus of interest was produced following fusion-fission reactions between a thick Al-27 target frame and a Hf-178 beam at a laboratory energy of 1150 MeV. This isomeric state is interpreted as an energetically favored, maximally aligned configuration of nu h (11/2) circle times pi(g (9/2))(2).

We revisit the problem of the kink in the charge radius shift of neutron-rich even isotopes near the N=126 shell closure. We show that the ability of a Skyrme force to reproduce the isotope shift is determined by the occupation of the neutron 1i11/2 orbital beyond N=126 and the corresponding change it causes to deeply-bound protons orbitals with a principal quantum number of 1. Given the observed position of the single-particle energies, one must either ensure occupation is allowed through correlations, or not demand that the single-particle energies agree with experimental values at the mean-field level.

Friction coefficients for the fusion reaction ¹⁶O+¹⁶O ’ ³²S are extracted based on both the time-dependent Hartree-Fock and the time-dependent density matrix methods. The latter goes beyond the mean-field approximation by taking into account the effect of two-body correlations, but in practical simulations of fusion reactions we find that the total energy is not conserved. We analyze this problem and propose a solution that allows for a clear quantification of dissipative effects in the dynamics. Compared to mean-field simulations, friction coefficients in the density-matrix approach are enhanced by about 20 %. An energy-dependence of the dissipative mechanism is also demonstrated, indicating that two-body collisions are more efficient at generating friction at low incident energies.