123628224
Competing fusion and quasifission reaction mechanisms in the production of superheavy nuclei
Within the framework of a dinuclear system model, a new master equation is constructed and solved, which includes the relative distance of nuclei as a new dynamical variable in addition to the mass asymmetry variable so that the nucleon transfer, which leads to fusion and the evolution of the relative distance, which leads to quasifission (QF) are treated simultaneously in a consistent way. The QF mass yields and evaporation residual cross sections to produce superheavy nuclei are systematically investigated under this framework. The results fit the experimental data well. It is shown that the Kramers formula gives results of QF, which agree with those by our diffusion treatment, only if the QF barrier is high enough. Otherwise some large discrepancies occur.
124058283
Dynamical deformation in heavy ion collisions and formation of superheavy nuclei
14590623
Nuclear structure of Hf-178 related to the spin-16, 31-year isomer
The projected shell model is used to study the multi-quasiparticle and collective excitations of Hf-178. With an axially symmetric basis, the spin-16 isomer at 2.4 MeV appears to be well separated in energy/spin space from other configurations. However, projected energy surface calculations suggest that Hf-178 has significant softness to axially asymmetric shapes, which can strongly modify the level distribution. The implications for photodeexcitation of the isomer are discussed. (C) 2004 Elsevier B.V. All rights reserved.
121260335
Weakly bound neutrons and quadrupole response function in the many-body pair correlation of neutron drip line nuclei
A simplified model of the Hartree-Fock Bogoliubov (HFB) equation with surface-type or volume-type pairing is solved in coordinate space with the correct asymptotic boundary conditions. By using the resulting HFB wavefunctions, the low-energy quadrupole (L = 2) response function is studied for the system with weakly bound s and d neutrons. As the binding energy of the neutrons becomes small or approaches zero, the discrete solutions of the HFB equation disappear. Then, without any further correlation ( for example, random phase approximation ( RPA) correlation), the threshold quadrupole response becomes broader and moves toward very low excitation energies, while the total strength increases very rapidly. The important role of the continuum character of the upper component u(lj) (r) of the HFB s(1/2) wavefunction in the increasing strength is pointed out. The large and broad quadrupole response with a very low peak energy is expected for neutron drip line nuclei with N approximate to 56 and Z approximate to 28, of which both the neutron 2d(5/2) and 3s(1/2) orbits may be weakly bound in the Hartree-Fock (HF) potential. (Less)
118278930
Tensor correlation, pairing interaction, and deformation in Ne isotopes and Ne hypernuclei
We study tensor and pairing effects on the quadruple deformation of neon isotopes based on a deformed Skyrme-Hartree-Fock model with BCS approximation for the pairing channel. We extend the SkyrmeHartree-Fock formalism for the description of single- and d ouble-lambda hypernuclei adopting two different hyperon-nucleon interactions. It is found that the inte rplay of pairing and tensor interactions is crucial to derive the deformations in several neon isotopes. Especi ally, the shapes of 26,30 Ne are studied in details in comparisons with experimentally observed shapes. Furthermore the deformations of the hypernuclei are compared with the corresponding neon isotopic cores in the presence of tensor force. We find the same shapes with somewhat smaller deformations for single Λ-hypernuclei compared with their core deformations. It is also pointed out that the latest version of hyper on interaction, the ESC08b model, having a deeper Λ potential makes smaller deformations for hypernuclei than those of another NSC97f model.
123014665
EFFECT OF TENSOR INTERACTION ON HEAVY AND SUPERHEAVY NUCLEI
The effect of tensor interaction is discussed on the deformation and the shell structure of heavy and superheavy nuclei within the deformed Skyrme Hartree-Fock+BCS model. The importance of the tensor correlations is shown for the single particle spectra of protons in 249Bk. The large shell gaps of superheavy nuclei are found at Z = 114 and Z = 120 for protons and N = 184 for neutrons with the spherical shape irrespective of the tensor correlations. It is also shown that Z = 114 and N = 164 shell gaps are more pronounced by the tensor correlations in the case of SLy5+T interaction.
51813822
Ionization structure and Fe K$\alpha$ energy for irradiated accretion disks
We study the radial ionization structure at the surface of an X-ray illuminated accretion disk. We plot the expected iron K$\alpha$ line energy as a function of the Eddington ratio and of the distance of the emitting matter from the central source, for a non-rotating and a maximally-rotating black hole. We compare the predicted disk line energies with those measured in an archival sample of active galactic nuclei observed with {\it Chandra}, {\it XMM-Newton} and {\it Suzaku}, and discuss whether the line energies are consistent with the radial distances inferred from reverberation studies. We also suggest using rapidly-variable iron K$\alpha$ lines to estimate the viscosity parameter of an accretion disk. There is a forbidden region in the line energy versus Eddington ratio plane, at low Eddington ratios, where an accretion disk cannot produce highly-ionized iron K$\alpha$ lines. If such emission is observed in low-Eddington-ratio sources, it is either coming from a highly-ionized outflow, or is a blue-shifted component from fast-moving neutral matter.