Nuclear Theory·nucl-th

Tuesday·July 4, 2017

13 papers—8 primary·5 cross-listed

01
Equilibrium nuclear ensembles taking into account vaporization of hot nuclei in dense stellar matter
Shun Furusawa · Igor Mishustin
We investigate the high-temperature effect on the nuclear matter that consists of mixture of nucleons and all nuclei in the dense and hot stellar environment. The individual nuclei are described within the compressible liquid-drop model that is based on Skyrme interactions for bulk energies and that takes into account modifications of the surface and Coulomb energies at finite temperatures and densities. The free-energy density is minimized with respect to the individual equilibrium densities of all heavy nuclei and the nuclear composition. We find that their optimized equilibrium densities become smaller and smaller at high temperatures because of the increase of thermal contributions to bulk free energies and the reduction of surface energies. The neutron-rich nuclei become unstable and disappear one after another at some temperatures. The calculations are performed for two sets of model parameters leading to different values of the slope parameter in the nuclear symmetry energy. It is found that the larger slope parameter reduces the equilibrium densities and the melting temperatures. We also compare the new model with some other approaches and find that the mass fractions of heavy nuclei in the previous calculations that omit vaporization are underestimated at $T ≲ 10$ MeV and overestimated at $T ≳ 10$ ~MeV. The further sophistication of calculations of nuclear vaporization and of light clusters would be required to construct the equation of state for explosive astrophysical phenomena.
nucl-thastro-ph.HEPRC(2018)·8 citations
02
Structure of krypton isotopes within the interacting boson model derived from the Gogny energy density functional
K. Nomura · R. Rodríguez-Guzmán · Y. M. Humadi · L. M. Robledo · H. Abusara
The evolution and coexistence of the nuclear shapes as well as the corresponding low-lying collective states and electromagnetic transition rates are investigated along the Krypton isotopic chain within the framework of the interacting boson model (IBM). The IBM Hamiltonian is determined through mean-field calculations based on the several parametrizations of the Gogny energy density functional and the relativistic mean-field Lagrangian. The mean-field energy surfaces, as functions of the axial $β$ and triaxial $γ$ quadrupole deformations, are mapped onto the expectation value of the interacting-boson Hamiltonian that explicitly includes the particle-hole excitations. The resulting boson Hamiltonian is then used to compute low-energy excitation spectra as well as E2 and E0 transition probabilities for $^{70 - 100}$ Kr. Our results point to a number of examples of the prolate-oblate shape transitions and coexistence both on the neutron-deficient and neutron-rich sides. A reasonable agreement with the available experimental data is obtained for the considered nuclear properties.
nucl-thnucl-exPRC(2017)·26 citations
03
Research on the halo in $^{31}$ Ne with complex momentum representation method
Ya-Juan Tian · Quan Liu · Tai-Hua Heng · Jian-You Guo
Halo is one of the most interesting phenomena in exotic nuclei especially for $^{31}$ Ne, which is deemed to be a halo nucleus formed by a $p -$ wave resonance. However, the theoretical calculations don't suggest a $p -$ wave resonance using the scattering phase shift approach or complex scaling method. Here, we apply the complex momentum representation method to explore resonances in $^{31}$ Ne. We have calculated the single-particle energies for bound and resonant states together with their evolutions with deformation. The results show that the $p -$ wave resonances appear clearly in the complex momentum plane accompanied with the $p - f$ inversion in the single-particle levels. As it happens the $p - f$ inversion, the calculated energy, width, and occupation probabilities of major components in the level occupied by valance neutron support a $p -$ wave halo for $^{31}$ Ne.
nucl-thnucl-exPRC(2017)·19 citations
04
General formalism of collective motion for any deformed system
Jian-You Guo
Based on Bohr model, we have presented a general formalism describing the collective motion for any deformed system, in which the collective Hamiltonian is expressed as vibrations in the body-fixed frame, rotation of whole system around the laboratory frame, and coupling between vibrations and rotation. Under the condition of decoupling approximation, we have derived the quantized Hamiltonian operator. Based on the operator, we have calculated the rotational spectra for some special octupole and hexadecapole deformed systems, and shown their dependencies on deformation. The result indicates that the contribution of octupole or hexadecapole deformations to the lowest band is regular, while that to higher bands is dramatic. These features reflecting octupole and hexadecapole deformations are helpful to recognize the properties of real nuclei with octupole and/or hexadecapole deformations coexisting with quadrupole deformations.
nucl-thnucl-exPRC(2015)·4 citations
05
The Spin and Orbital Contributions to Magnetic Dipole Transitions
Arun Kingan · Michael Quinonez · Xiaofei Yu · Larry Zamick
In previous works we examined they systematics of magnetic dipole transitions in a single j shell. We here extend the study to large space calculations.We consider the nuclei $^{44}$ Ti, $^{46}$ Ti and $^{48}$ C. Of particular interest is the contributions to B(M1) of the spin and orbital parts of the magnetic dipole operator. Whereas usual scissors mode analyses have as an initial state the J=0+ ground state (of an even-even nucleus) we here start with the lowest J=1+ T=1 state. This enables us to reach many more states e.g. J=2,T=0,1, and 2 and thus getter a better picture of the collectivity of this state.
nucl-thnucl-exIJMPE(2018)·9 citations
06
Semiclassical triton
Nishchal R. Dwivedi · Harjeet Kaur · Sudhir R. Jain
The symmetric components of the spatial part of $S$ - and $D$ - states' wavefunctions for triton $(^{3} H)$ are investigated utilizing semiclassical expansion (in the powers of $ℏ$ ). Analysis of the diagonalized Hamiltonian reveals the existence of two different mass states within the ground state of triton. We have solved the coupled differential equations for the two admixed states $^{2} S_{1/2}$ and $^{4} D_{1/2}$ owing to tensor interactions exploiting classical WKB-theory using phenomenological Feshbach-Pease potentials. The relative probability of the $D$ -state is found to be in good agreement with the experimentally inferred value (4 - 5 \%).
nucl-thEPJA(2018)·7 citations
07
Odd J states of isospin zero and one for 4 nucleon systems: near degeneracies
Arun Kingan · Larry Zamick
In this work we calculate the energies odd J $^{+}$ states in selectedeven-even nuclei- $^{44}$ Ti $^{52}$ Fe and $^{96}$ Cd. Of particularinterest is the fact that in many cases the first T=0 and the first T=1 state are close in energy. Whether the lowest odd J state hasT=0 or T=1 is here considered.
nucl-thnucl-exPRC(2018)·1 citation
08
Smoothed square well potential
Péter Salamon · Tamás Vertse
The classical square well potential is smoothed with a finite range smoothing function in order to get a new simple strictly finite range form for the phenomenological nuclear potential. The smoothed square well form becomes exactly zero smoothly at a finite distance, in contrast to the Woods-Saxon form. If the smoothing range is four times the diffuseness of the Woods-Saxon shape both the central and the spin-orbit terms of the Woods-Saxon shape are reproduced reasonably well. The bound single particle energies in a Woods-Saxon potential can be well reproduced with those in the smoothed square well potential. The same is true for the complex energies of the narrow resonances.
nucl-thEPJA(2017)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE