P. D. Stevenson

The TDHF code Sky3D

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.

Fission dynamics within time-dependent Hartree-Fock: Deformation-induced fission

Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products.Purpose: We explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide

Spin-Excitation Mechanisms in Skyrme-Force Time-Dependent Hartree-Fock

^{240}\text{Pu}

Unrestricted Skyrme-tensor time-dependent Hartree-Fock model and its application to the nuclear response from spherical to triaxial nuclei

as an example.Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate nonadiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data.Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behavior. Those beginning just beyond the barrier explore large-amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation.Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

Density distributions of superheavy nuclei

We investigate the role of odd-odd (with respect to time inversion) couplings in the Skyrme force on collisions of light nuclei, employing a fully three-dimensional numerical treatment without any symmetry restrictions and with modern Skyrme functionals. We demonstrate the necessity of these couplings to suppress spurious spin excitations owing to the spin-orbit force in free translational motion of a nucleus but show that in a collision situation there is a strong spin excitation even in spin-saturated systems which persists in the departing fragments. The energy loss is considerably increased by the odd-odd terms.

Nuclear charge radii and electromagnetic moments of radioactive scandium isotopes and isomers

The nuclear time-dependent Hartree-Fock model formulated in three-dimensional space, based on the full standard Skyrme energy density functional complemented with the tensor force, is presented. Full self-consistency is achieved by the model. The application to the isovector giant dipole resonance is discussed in the linear limit, ranging from spherical nuclei (16O and 120Sn) to systems displaying axial or triaxial deformation (24Mg, 28Si, 178Os, 190W and 238U). Particular attention is paid to the spin-dependent terms from the central sector of the functional, recently included together with the tensor. They turn out to be capable of producing a qualitative change on the strength distribution in this channel. The effect on the deformation properties is also discussed. The quantitative effects on the linear response are small and, overall, the giant dipole energy remains unaffected. Calculations are compared to predictions from the (quasi)-particle random-phase approximation and experimental data where available, finding good agreement

Reaction cross-sections for light nuclei on 12C using relativistic mean field formalism

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 Pb-208. The ground-state deformations, nuclear radii, neutron-skin thicknesses and alpha-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 (292)120 nucleus. Earlier predictions of remarkably low central density are not supported when deformation is allowed for.

Spectroscopic calculations of the low-lying structure in exotic Os and W isotopes

Collinear laser spectroscopy experiments with the Sc+ transition 3d4s 3D2 → 3d4p 3F3 at λ = 363.1 nm were performed on the 42–46Sc isotopic chain using an ion guide isotope separator with a cooler-buncher. Nuclear magnetic dipole and electric quadrupole moments as well as isotope shifts were determined from the hyperfine structure for five ground states and two isomers. Extensive multi-configurational Dirac–Fock calculations were performed in order to evaluate the specific mass-shift, MSMS, and field-shift, F, parameters which allowed evaluation of the charge radii trend of the Sc isotopic sequence. The charge radii obtained show systematics more like the Ti radii, which increase towards the neutron shell closure N = 20, than the symmetric parabolic curve for Ca. The changes in mean-square charge radii of the isomeric states relative to the ground states for 44Sc and 45Sc were also extracted. The charge radii difference between the ground and isomeric states of 45Sc is in agreement with the deformation effect estimated from the B(E2) measurements but is smaller than the deformation extracted from the spectroscopic quadrupole moments.

The effect of the tensor force on the predicted stability of superheavy nuclei

The reaction cross-sections are calculated for various Li, Be and B+12C systems, also involving the exotic halo nuclei, by using both the spherical and deformed relativistic mean field (RMF) densities in the finite range Glauber model with Coulomb effects included. For reactions at higher energies (>500 MeV/nucleon), both the spherical and deformed RMF densities give similar results for all the isotopic chains of exotic nuclei studied here. On the other hand, for reactions between stable nuclei, though the two RMF densities (spherical and deformed) result in simply an overall normalization for the excitation functions, it gives an improved comparison with experimental data, at high and low energies for spherical and deformed densities, respectively. A similar normalization is obtained for other densities, which means to stress that, though densities are different, they do not change much with the excitation energy. Finally, some details of the characteristic properies of exotic light nuclei are shown to contain the deformation effects of the halo nuclei.

The influence of the symmetry energy on the giant monopole resonance of neutron-rich nuclei analyzed in Thomas–Fermi theory

This work was supported in part by grants-in-aid for Scientific Research (A) 20244022 and No. 217368 and by the JSPS Core-to-Core Program EFES. K. N. is supported by the JSPS. P. H. R., Z. P., and P. D. S. acknowledge financial support from STFC(UK). Thework of L. M. R., P. S., and R. R. has been supported byMICINN (Spain) under research Grants No. FIS2008-01301, No. FPA2009-08958, and No. FIS2009- 07277, as well as by Consolider-Ingenio 2010 Programs CPAN CSD2007-00042 and MULTIDARK CSD2009-00064