arXiv subjects

Kazuhiro Yabana

Publications and source records attributed to Kazuhiro Yabana.

At least 73 records · Page 4Linked to original sources

arXiv2006

Real-time Skyrme TDHF dynamics of giant resonances

Nuclear dynamics of giant resonances are investigated with the real-time Skyrme TDHF method. The TDHF equation is explicitly linearized with respect to variation of single-particle wave functions. The time evolution of transition densities are calculated for giant dipole resonances. The time-dependent densities of protons and neutrons suggest that the dynamics of giant dipole resonance in neutron-rich nuclei are significantly different from that in stable nuclei with N=Z.

nucl-th↗

arXiv2006

Nuclear dynamics in time-dependent picture

Using the time-dependent theory of quantum mechanics, we investigate nuclear electric dipole responses. The time evolution of a wave function is explicitly calculated in the coordinate-space representation. The particle continuum is treated with the absorbing boundary condition. Calculated time-dependent quantities are transformed into those of familiar energy representation. We apply the method to a three-body model for 11Li and to the mean-field model for 22O, then discuss properties of E1 response.

nucl-th↗

arXiv2006

Parity-projected Skyrme Hartree-Fock and angular momentum projection approach to Mg isotopes

We perform calculations of the variation after parity projection with Skyrme interaction for ground and excited states of even-even Mg isotopes. Using the 3D real-space representation, we can take into account any kind of deformation; e.g., cluster structure, gamma-deformation. We also perform the full 3D angular momentum projection to obtained rotational spectra and B(E2). In 24Mg, the ground K^pi=0+ and several odd-parity bands are calculated. In 30,32,34Mg, our calculation reproduces a breaking of the N=20 magic number, so-called "Island of inversion" phenomena. Properties of both the ground and excited states are reasonably reproduced.

nucl-th↗

arXiv2006

Suppressed fusion cross section for neutron halo nuclei

Fusion reactions of neutron-halo nuclei are investigated theoretically with a three-body model. The time-dependent wave-packet method is used to solve the three-body Schrodinger equation. The halo neutron behaves as a spectator during the Coulomb dissociation process of the projectile. The fusion cross sections of 11Be-209Bi and 6He-238U are calculated and are compared with measurements. Our calculation indicates that the fusion cross section is slightly hindered by the presence of weakly bound neutrons.

nucl-th↗

arXiv2004

Linear response theory in the continuum for deformed nuclei: Green's function vs. time-dependent Hartree-Fock with the absorbing-boundary condition

The continuum random-phase approximation is extended to the one applicable to deformed nuclei. We propose two different approaches. One is based on the use of the three dimensional (3D) Green's function and the other is the small-amplitude TDHF with the absorbing-boundary condition. Both methods are based on the 3D Cartesian grid representation and applicable to systems without any symmetry on nuclear shape. The accuracy and identity of these two methods are examined with the BKN interaction. Using the full Skyrme energy functional in the small-amplitude TDHF approach, we study the isovector giant dipole states in the continuum for O-16 and for even-even Be isotopes.

nucl-th↗

arXiv2004

Variation after parity projection calculation with Skyrme interaction for light nuclei

A self-consistent calculation with variation after parity projection is proposed to study both ground and excited states of light nuclei. This procedure provides description of the ground state incorporating some correlation effects, and self-consistent solutions for the excited states of negative parity. For flexible description of nuclear shapes, single particle orbitals are represented on a uniform grid in the three-dimensional Cartesian coordinates. The angular momentum projection is performed after variation to calculate rotational spectra. To demonstrate the usefulness of the method, results are shown for two N=Z nuclei, 20Ne and 12C, for which clustering correlations are known to be important. In the 20Ne nucleus, both cluster-like and shell-model-like states are described simultaneously in the present framework. For 12C nucleus, the appearance of three-alpha clustering correlation in the ground state is investigated in relation to the strength of the two-body spin-orbit interaction.

nucl-th↗

arXiv2003

Continuum Response and Reaction in Neutron-Rich Be Nuclei

We study E1 resonances, breakup and fusion reactions for weakly bound Be nuclei. The absorbing-boundary condition (ABC) is used to describe both the outgoing and incoming boundary conditions. The neutron continuum plays important roles in response and reaction of neutron drip-line nuclei.

nucl-th↗

arXiv2003

Response in the continuum for light deformed neutron-rich nuclei

The time-dependent Hartree-Fock calculation with a full Skyrme energy functional has been carried out on the three-dimensional Cartesian lattice space to study E1 giant dipole resonances (GDR) in light nuclei. The outgoing boundary condition for the continuum states is treated by the absorbing complex potential. The calculation for GDR in O-16 suggests a significant influence of the residual interaction associated with time-odd densities in the Skyrme functional. We also predict a large damping for superdeformed Be-14 at the neutron drip line.

nucl-th↗

arXiv2003

Oscillator strength distribution in C3H6 isomers studied with the time-dependent density functional method in the continuum

We present photoabsorption oscillator strengths for C3H6 molecules with emphasis on the difference between isomers, cyclopropane and propylene. We use an iterative numerical method based on the time-dependent local density approximation with continuum, which we have recently developed. The oscillator strengths for the two isomers differ at photon energies above their ionization thresholds. The magnitude and the shape of the oscillator strength distribution are in good agreement with recent experiments. The differences between the isomers arise from difference in symmetry of electronic states and different behaviors of continuum excitations.

physics.chem-ph↗

arXiv2003

Time-dependent wave-packet approach for fusion reactions of halo nuclei

The fusion reaction of a halo nucleus 11Be on 208Pb is described by a three-body direct reaction model. A time-dependent wave packet approach is applied to a three-body reaction problem. The wave packet approach enables us to obtain scattering solutions without considering the three-body scattering boundary conditions. The time evolution of the wave packet also helps us to obtain intuitive understanding of the reaction dynamics. The calculations indicate a decrease of the fusion probability by the presence of the halo neutron.

nucl-th↗

arXiv2002

Absorbing-boundary-condition method for drip-line nuclei

Absorbing-boundary-condition method and its applications to nuclear responses and breakup reactions are reported. The method facilitates calculations of the continuum states in the coordinate space of many degrees of freedom. Properties of nuclei near drip lines are discussed.

nucl-th↗

arXiv2002

Application of Absorbing Boundary Condition to Nuclear Breakup Reactions

Absorbing boundary condition approach to nuclear breakup reactions is investigated. A key ingredient of the method is an absorbing potential outside the physical area, which simulates the outgoing boundary condition for scattered waves. After discretizing the radial variables, the problem results in a linear algebraic equation with a sparse coefficient matrix, to which efficient iterative methods can be applicable. No virtual state such as discretized continuum channel needs to be introduced in the method. Basic aspects of the method are discussed by considering a nuclear two-body scattering problem described with an optical potential. We then apply the method to the breakup reactions of deuterons described in a three-body direct reaction model. Results employing the absorbing boundary condition are found to accurately coincide with those of the existing method which utilizes discretized continuum channels.

nucl-th↗

arXiv2002

Giant resonances in the deformed continuum

Giant resonances in the continuum for deformed nuclei are studied with the time-dependent Hartree-Fock (TDHF) theory in real time and real space. The continuum effect is effectively taken into account by introducing a complex Absorbing Boundary Condition (ABC).

nucl-th↗

arXiv2002

Atomic spectra in a helium bubble

Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describing spectral perturbations in more complex environments.

nucl-th↗

arXiv2002

Absorbing Boundary Condition Approach for Breakup Reactions of Halo Nuclei

Application of the absorbing boundary condition is discussed to analyse breakup reactions of weakly bound nuclei. The key ingredient is an introduction of the absorbing potential outside the physical area which simulates the outgoing boundary condition approximately. The scattering problem is then recasted into the Schroedinger like equation with a source term in the interaction region and with the vanishing boundary condition at the boundary. We demonstrate usefulness of the method taking a few examples. Deuteron breakup reactions are examined comparing present results with those by the continuum-discretized coupled-channel method. We next discuss the breakup reactions of single-neutron halo nucleus, 11Be.

nucl-th↗

arXiv2002

3D Real-Space Calculation of the Continuum Response

We present that a linear response theory in the continuum can be easily formulated with Absorbing Boundary Condition (ABC). The theory is capable of describing continuum spectra and dynamical correlations. Application of the ABC does not require the spherical symmetry and the method is suitable for mesh representation in the real coordinate space. Isovector giant dipole resonances in beryllium isotopes are studied with the time-dependent Hartree-Fock with the Skyrme force in a three-dimensional mesh space with the ABC.

nucl-th↗

arXiv2001

Application of density functional theory to line broadening: Cs atoms in liquid helium

We test the applicability of density functional theory (DFT) to spectral perturbations taking an example of a Cs atom surrounded by superfluid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describing spectral perturbations in more complex environments.

physics.atom-ph↗

arXiv2001

3D real-space calculations of continuum response

We present linear response theories in the continuum capable of describing continuum spectra and dynamical correlations of finite systems with no spatial symmetry. Our formulation is essentially the same as the continuum random-phase approximation (RPA) but suitable for uniform grid representation in the three-dimensional (3D) Cartesian coordinate. Effects of the continuum are taken into account by solving equations iteratively with a retarded Green's function. The method is applied to photoabsorption spectra in small molecules (acetylene and ethylene) and inelastic electron scattering from a deformed nucleus 12C.

nucl-th↗