Deformed quasiparticle-random-phase approximation for neutron-rich nuclei using the Skyrme energy density functional

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Giant multipole resonances in Nd and Sm isotopes are studied by employing the quasiparticle-random-phase approximation on the basis of the Skyrme energy-density-functional method. Deformation effects on giant resonances are investigated in these isotopes which manifest a typical nuclear shape change from spherical to prolate shapes. The peak energy, the broadening, and the deformation splitting of the isoscalar giant monopole (ISGMR) and quadrupole (ISGQR) resonances agree well with measurements. The magnitude of the peak splitting and the fraction of the energy-weighted strength in the lower peak of the ISGMR reflect the nuclear deformation. The experimental data on ISGMR, ISGDR, and ISGQR are consistent with the nuclear-matter incompressibility $K \simeq 210-230$ MeV and the effective mass $m^*_0/m \simeq 0.8-0.9$. However, the high-energy octupole resonance (HEOR) in $^{144}$Sm seems to indicates a smaller effective mass, $m^*_0/m \simeq 0.7-0.8$. A further precise measurement of HEOR is desired to determine the effective mass.Comment: Submitted to Phys. Rev.

Section: B Mixing Of Spurious Center-of-mass Motionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shape evolution of giant resonances in Nd and Sm isotopes

Yoshida

Nakatsukasa

2013

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“…The axially deformed QRPA calculations with the modern Skyrme, Gogny, and covariant EDFs have recently become available [19][20][21][22][23], and the 3D RPA calculations without pairing were achieved [24][25][26][27]. However, currently, an efficient framework to solve the self-consistent QRPA with modern EDFs applicable to triaxial shapes is still missing, although there are some related studies using the real-time method [28][29][30][31][32].…”

mentioning

confidence: 99%

Multipole modes of excitation in triaxially deformed superfluid nuclei

Washiyama

Nakatsukasa

2017

Background:The five-dimensional quadrupole collective model based on energy density functionals (EDFs) has often been employed to treat long-range correlations associated with shape fluctuations in nuclei. Our goal is to derive the collective inertial functions in the collective Hamiltonian by the local quasiparticle random-phase approximation (QRPA) that correctly takes into account time-odd mean-field effects. Currently, a practical framework to perform the QRPA calculation with the modern EDFs on the (β,γ ) deformation space is not available. Purpose: Toward this goal, we develop an efficient numerical method to perform the QRPA calculation on the (β,γ ) deformation space based on the Skyrme EDF. Methods: We use the finite amplitude method (FAM) for the efficient calculation of QRPA strength functions for multipole external fields. We construct a computational code of FAM-QRPA in the three-dimensional Cartesian coordinate space to handle triaxially deformed superfluid nuclei. Introduction. The shape of atomic nuclei is influenced strongly by the quantum nature of nuclear systems. Excitation spectra and their transition probabilities clearly indicate the existence of shape fluctuations and shape coexistence [1], particularly in transitional regions from spherical to deformed shapes in the ground state. The long-lived fission products (LLFP) from uranium fueled reactors, such as Pd and Zr isotopes, are located in transitional regions on the nuclear chart and demonstrate the shape mixing and coexistence. It is important to understand the basic properties of the LLFPs to develop a possible nuclear transmutation method, which is the main target of an ImPACT program "Reduction and Resource Recycling of High-level Radioactive Wastes through Nuclear Transmutation" [2].One of the standard methods of investigating nuclear manybody problems is the nuclear energy density functional (EDF) theory [3]. The nuclear EDF well describes the ground-state properties of atomic nuclei. However, on the mean-field level, it cannot describe shape fluctuations and shape coexistence. We need to go beyond the mean field for a description of such phenomena, including quantum fluctuations associated with the large-amplitude collective motion. If the EDF were constructed as an expectation value of a well-defined Hamiltonian, a possible extension would be the generator coordinate method (GCM) [4][5][6]. However, most of the EDFs are known to have a singular behavior [7,8], which prevents us from the straightforward application of the GCM.

“…The experiment performed at RIKEN reported the PDR of 26 Ne around E x = 9 MeV with the integrated E1 strength of B(E1) = 0.49 ± 0.16 e 2 fm 2 which exhausts approximately 5% of the Thomas-ReicheKuhn (TRK) sum rule [14]. Many theoretical studies based on the quasiparticle random phase approximation (QRPA) have been performed and have successfully described these observed properties, although the results range between E x = 6-10 MeV and 5%-10% of the TRK sum rule depending on the effective interactions used in the calculations [10,[15][16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Structure and decay of the pygmy dipole resonance in Ne26

Kimura

2017

The low-lying spectra of 24,25,26 Ne and the structure of the pygmy dipole resonance (PDR) in 26 Ne have been theoretically studied by the antisymmetrized molecular dynamics (AMD) and its extended version called shifted-basis AMD. The calculated energy and strength of the PDR reasonably agree with the observation, and the analysis of the wave function shows that the PDR is dominated by neutron excitation coupled to the quadrupole excited core nucleus 25 Ne, which explains the observed unexpected decay of PDR to the excited states of 25 Ne. The large isoscalar component of PDR is also shown and the enhancement of the core excitation in neutron-rich Ne isotopes is conjectured.