86 research outputs found
Relativistic mean field study of the properties of Z=117 nucleus and the decay chains of 117 isotopes
We have calculated the binding energy, root-mean-square radius and quadrupole
deformation parameter for the recently synthesized superheavy element Z=117,
using the axially deformed relativistic mean field (RMF) model. The calculation
is extended to various isotopes of Z=117 element, strarting from A=286 till
A=310. We predict almost spherical structures in the ground state for almost
all the isotopes. A shape transition appears at about A=292 from prolate to a
oblate shape structures of Z=117 nucleus in our mean field approach. The most
stable isotope (largest binding energy per nucleon) is found to be the
117 nucleus. Also, the Q-value of -decay and the
half-lives are calculated for the -decay chains of
117 and 117, supporting the magic numbers at N=172 and/ or 184.Comment: 6 Pages and 8 Figure
Particle transfer and fusion cross-section for Super-heavy nuclei in dinuclear system
Within the dinuclear system (DNS) conception, instead of solving
Fokker-Planck Equation (FPE) analytically, the Master equation is solved
numerically to calculate the fusion probability of super-heavy nuclei, so that
the harmonic oscillator approximation to the potential energy of the DNS is
avoided. The relative motion concerning the energy, the angular momentum, and
the fragment deformation relaxations is explicitly treated to couple with the
diffusion process, so that the nucleon transition probabilities, which are
derived microscopically, are time-dependent. Comparing with the analytical
solution of FPE, our results preserve more dynamical effects. The calculated
evaporation residue cross sections for one-neutron emission channel of Pb-based
reactions are basically in agreement with the known experimental data within
one order of magnitude.Comment: 19 pages, plus 6 figures, submitted to Phys. Rev.
Superdeformed and Hyperdeformed States in Z=122 Isotopes
We calculate the binding energy, root-mean-square radius and quadrupole
deformation parameter for the recent, 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 isotopes of Z=122 element, strarting from A=282 to
A=320. We predict highly deformed structures in the ground state 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 mean field approaches. The
most stable isotope (largest binding energy per nucleon) is found to be
122, instead of the experimentally observed 122.Comment: 7 pages 8 Figures 2 Tabl
Prospects for the discovery of the next new element: Influence of projectiles with Z > 20
The possibility of forming new superheavy elements with projectiles having Z
> 20 is discussed. Current research has focused on the fusion of 48Ca with
actinides targets, but these reactions cannot be used for new element
discoveries in the future due to a lack of available target material. The
influence on reaction cross sections of projectiles with Z > 20 have been
studied in so-called analog reactions, which utilize lanthanide targets
carefully chosen to create compound nuclei with energetics similar to those
found in superheavy element production. The reactions 48Ca, 45Sc, 50Ti, 54Cr +
159Tb, 162Dy have been studied at the Cyclotron Institute at Texas A&M
University using the Momentum Achromat Recoil Spectrometer. The results of
these experimental studies are discussed in terms of the influence of
collective enhancements to level density for compound nuclei near closed
shells, and the implications for the production of superheavy elements. We have
observed no evidence to contradict theoretical predictions that the maximum
cross section for the 249Cf(50Ti, 4n)295120 and 248Cm(54Cr, 4n)298120 reactions
should be in the range of 10-100 fb.Comment: An invited talk given by Charles M. Folden III at the 11th
International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio,
Texas, USA, May 27-June 1, 2012. Also contains information presented by
Dmitriy A. Mayorov and Tyler A. Werke in separate contributions to the
conference. This contribution will appear in the NN2012 Proceedings in
Journal of Physics: Conference Series (JPCS
Density Dependent Hadron Field Theory
A fully covariant approach to a density dependent hadron field theory is
presented. The relation between in--medium NN interactions and
field--theoretical meson--nucleon vertices is discussed. The medium dependence
of nuclear interactions is described by a functional dependence of the
meson--nucleon vertices on the baryon field operators. As a consequence, the
Euler--Lagrange equations lead to baryon rearrangement self--energies which are
not obtained when only a parametric dependence of the vertices on the density
is assumed. It is shown that the approach is energy--momentum conserving and
thermodynamically consistent. Solutions of the field equations are studied in
the mean--field approximation. Descriptions of the medium dependence in terms
of the baryon scalar and vector density are investigated. Applications to
infinite nuclear matter and finite nuclei are discussed. Density dependent
coupling constants obtained from Dirac--Brueckner calculations with the Bonn
NN-potentials are used. Results from Hartree calculations for energy spectra,
binding energies and charge density distributions of , and
are presented. Comparisons to data strongly support the importance
of rearrangement in a relativistic density dependent field theory. Most
striking is the simultanuous improvement of charge radii, charge densities and
binding energies. The results indicate the appearance of a new "Coester line"
in the nuclear matter equation of state.Comment: 48 LateX pages, 12 Figures, figures and full paper are available as
postscript files by anonymous ftp at ftp://theorie.physik.uni-giessen.de/dd
Magic numbers for superheavy nuclei in relativistic continuum Hartree-Bogoliubov theory
The magic proton and neutron numbers are searched in the superheavy region
with proton number =100 - 140 and neutron number = (+30) - (2+32)
by the relativistic continuum Hartree-Bogoliubov (RCHB) theory with
interactions NL1, NL3, NLSH, TM1, TW99, DD-ME1, PK1, and PK1R. Based on the
two-nucleon separation energies and , the two-nucleon gaps
and , the shell correction energies
and , the pairing energies and ,
and the pairing gaps and , =120, 132, and 138 and
=172, 184, 198, 228, 238, and 258 are suggested to be the magic numbers
within the present approach. The -decay half-lives are also discussed.
In addition, the potential energy surfaces of possible doubly magic nuclei are
obtained by the deformation-constrained relativistic mean field (RMF) theory,
and the shell effects stabilizing the nuclei are investigated. Furthermore, the
formation cross sections of 120 and 120 at the
optimal excitation energy are estimated by a phenomenological cold fusion
reactions model with the structure information extracted from the constrained
RMF calculation.Comment: 37 pages, 14 figure
Shell Structure of the Superheavy Elements
Ground state properties of the superheavy elements (SHE) with Z from 108 to
128 and N from 150 to 192 are investigated using both the Skyrme-Hartree-Fock
method with a density-independent contact pairing interaction and the
macroscopic-microscopic approach with an average Woods-Saxon potential and a
monopole pairing interaction. Detailed analysis of binding energies, separation
energies, shell effects, single proton and neutron states, equilibrium
deformations, alpha-decay energies, and other observables is given.Comment: 27 RevTeX pages, 22 figures available upon request to
[email protected]
Ground state properties and bubble structure of superheavy nuclei
We calculate the ground state properties of recently synthesized superheavy
nuclei starting from =105-120. The nonrelativistic and relativistic mean
field formalisms is used to evaluate the binding energy, charge radius,
quadrupole deformation parameter and the density distribution of nucleons. We
analyzed the stability of the nuclei based on the binding energy and neutron to
proton ratio. We also studied the bubble structure of the nucleus which reveals
about the special features of the superheavy nucleus
Shell Corrections of Superheavy Nuclei in Self-Consistent Calculations
Shell corrections to the nuclear binding energy as a measure of shell effects
in superheavy nuclei are studied within the self-consistent Skyrme-Hartree-Fock
and Relativistic Mean-Field theories. Due to the presence of low-lying proton
continuum resulting in a free particle gas, special attention is paid to the
treatment of single-particle level density. To cure the pathological behavior
of shell correction around the particle threshold, the method based on the
Green's function approach has been adopted. It is demonstrated that for the
vast majority of Skyrme interactions commonly employed in nuclear structure
calculations, the strongest shell stabilization appears for Z=124, and 126, and
for N=184. On the other hand, in the relativistic approaches the strongest
spherical shell effect appears systematically for Z=120 and N=172. This
difference has probably its roots in the spin-orbit potential. We have also
shown that, in contrast to shell corrections which are fairly independent on
the force, macroscopic energies extracted from self-consistent calculations
strongly depend on the actual force parametrisation used. That is, the A and Z
dependence of mass surface when extrapolating to unknown superheavy nuclei is
prone to significant theoretical uncertainties.Comment: 14 pages REVTeX, 8 eps figures, submitted to Phys. Rev.
Relativistic Continuum Hartree Bogoliubov Theory for Ground State Properties of Exotic Nuclei
The Relativistic Continuum Hartree-Bogoliubov (RCHB) theory, which properly
takes into account the pairing correlation and the coupling to (discretized)
continuum via Bogoliubov transformation in a microscopic and self-consistent
way, has been reviewed together with its new interpretation of the halo
phenomena observed in light nuclei as the scattering of particle pairs into the
continuum, the prediction of the exotic phenomena -- giant halos in nuclei near
neutron drip line, the reproduction of interaction cross sections and
charge-changing cross sections in light exotic nuclei in combination with the
Glauber theory, better restoration of pseudospin symmetry in exotic nuclei,
predictions of exotic phenomena in hyper nuclei, and new magic numbers in
superheavy nuclei, etc. Recent investigations on new effective interactions,
the density dependence of the interaction strengthes, the RMF theory on the
Woods-Saxon basis, the single particle resonant states, and the resonant BCS
(rBCS) method for the pairing correlation, etc. are also presented in some
details.Comment: 79 pages. Prog. Part. Nucl. Phys. (2005) in pres
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