71 research outputs found
The Triaxial Rotation Vibration Model in the Xe-Ba Region
The axial Rotation Vibration Model is here extended to describe also triaxial
equilibrium shapes with beta and gamma vibrations allowing for the interaction
between vibrations and rotations. This Triaxial Rotation Vibration Model (TRVM)
is applied to Xe and Ba isotopes with mass numbers between 120 and 130. This
area has recently been pointed out to be the O(6) limit of the Interacting
Boson Approximation (IBA). The present work shows that the TRVM can equally
well describe these nuclei concerning their excitation energies and E2
branching ratios.Comment: 11 pages, 2 figure
E(5), X(5), and Prolate to Oblate Shape Phase Transitions in Relativistic Hartree Bogoliubov Theory
Relativistic mean field theory with the NL3 force is used for producing
potential energy surfaces (PES) for series of isotopes suggested as exhibiting
critical point symmetries. Relatively flat PES are obtained for nuclei showing
the E(5) symmetry, while in nuclei corresponding to the X(5) case, PES with a
bump are obtained. The PES corresponding to the Pt chain of isotopes suggest a
transition from prolate to oblate shapes at 186-Pt.Comment: 21 pages, LaTeX, including 14 .eps figure
Lifetime Measurements in 120Xe
Lifetimes for the lowest three transitions in the nucleus Xe have
been measured using the Recoil Distance Technique. Our data indicate that the
lifetime for the transition is more than a factor of
two lower than the previously adopted value and is in keeping with more recent
measurements performed on this nucleus. The theoretical implications of this
discrepancy and the possible reason for the erroneous earlier results are
discussed. All measured lifetimes in Xe, as well as the systematics of
the lifetimes of the 2 states in Xe isotopes, are compared with
predictions of various models. The available data are best described by the
Fermion Dynamic Symmetry Model (FDSM).Comment: 9 pages, RevTeX, 3 figures with Postscript file available on request
at [email protected], [email protected]. Submitted to Phys.
Rev.
Systematic studies of binding energy dependence of neutron - proton momentum correlation function
Hanbury Brown-Twiss (HBT) results of the neutron-proton correlation function
have been systematically investigated for a series nuclear reactions with light
projectiles with help of Isospin-Dependent Quantum Molecular Dynamics model.
The relationship between the binding energy per nucleon of the projectiles and
the strength of the neutron-proton HBT at small relative momentum has been
obtained. Results show that neutron-proton HBT results are sensitive to the
binding energy per nucleon.Comment: 10 pages, 5 figures; accepted by Journal of Physics G: Nuclear and
Particle Physic
Vortex arrays in neutral trapped Fermi gases through the BCS–BEC crossover
Vortex arrays in type-II superconductors reflect the translational symmetry of an infinite system. There are cases, however, such as ultracold trapped Fermi gases and the crust of neutron stars, where finite-size effects make it complex to account for the geometrical arrangement of vortices. Here, we self-consistently generate these arrays of vortices at zero and finite temperature through a microscopic description of the non-homogeneous superfluid based on a differential equation for the local order parameter, obtained by coarse graining the Bogoliubov–de Gennes (BdG) equations. In this way, the strength of the inter-particle interaction is varied along the BCS–BEC crossover, from largely overlapping Cooper pairs in the Bardeen–Cooper–Schrieffer (BCS) limit to dilute composite bosons in the Bose–Einstein condensed (BEC) limit. Detailed comparison with two landmark experiments on ultracold Fermi gases, aimed at revealing the presence of the superfluid phase, brings out several features that make them relevant for other systems in nature as well
Quantum Tunneling in Nuclear Fusion
Recent theoretical advances in the study of heavy ion fusion reactions below
the Coulomb barrier are reviewed. Particular emphasis is given to new ways of
analyzing data, such as studying barrier distributions; new approaches to
channel coupling, such as the path integral and Green function formalisms; and
alternative methods to describe nuclear structure effects, such as those using
the Interacting Boson Model. The roles of nucleon transfer, asymmetry effects,
higher-order couplings, and shape-phase transitions are elucidated. The current
status of the fusion of unstable nuclei and very massive systems are briefly
discussed.Comment: To appear in the January 1998 issue of Reviews of Modern Physics. 13
Figures (postscript file for Figure 6 is not available; a hard copy can be
requested from the authors). Full text and figures are also available at
http://nucth.physics.wisc.edu/preprints
Description of Even-Even Xe isotopes in the transitional region of IBM
Properties of Xe isotopes isotopes are studied in the U(5)O(6)
transitional region of Interacting Boson Model (IBM-1). The energy levels and
B(E2)transition rates are calculated via the affine SU(1,1)Lie Algebra. The
agreement with the most recent experimental is acceptable. The evaluated
Hamiltonian control parameters suggest a spherical to (/gamma)-soft shape
transition and propose the Xe(A=130)nucleus as the best candidate for the
E(5)symmetry.Comment: 15 pages,3 figures. I have received an email from the BJPH editor
(Prof.Luiz Nunes de Oliveira)which order me to resubmit the final version of
paper and note that, paper will appear in Volume 43 of the Brazilian Journal
of Physic
The (n, gamma) campaigns at EXILL
At the PF1B cold neutron beam line at the Institut Laue Langevin, the EXILL array consisting of EXOGAM, GASP and ILL-Clover detectors was used to perform (n, gamma) measurements at very high coincidence rates. About ten different reactions were measured in autumn 2012 using a highly collimated cold neutron beam. In spring 2013, the EXOGAM array was combined with 16 LaBr3(Ce) scintillators in the EXILL&FATIMA campaign for the measurement of lifetimes using the generalised centroid difference method. We report on the properties of the set-ups and present first results from both campaigns
Seismicity at the convergent plate boundary offshore Crete, Greece, observed by an amphibian network
- …