Low-lying dipole response in the stable<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mrow><mml:mn>40</mml:mn><mml:mo>,</mml:mo><mml:mn>48</mml:mn></mml:mrow></mml:msup></mml:math>Ca nuclei with the second random-phase approximation

Gambacurta, D.; Grasso, M.; Catara, F.

doi:10.1103/physrevc.84.034301

Cited by 67 publications

(77 citation statements)

References 56 publications

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“…There are some calculations beyond the (Q)RPA as well [44][45][46][47][48][49]. However, even in the (Q)RPA level, different models often predict different properties.…”

Section: Introductionmentioning

confidence: 99%

Systematic investigation of low-lying dipole modes using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory

2014

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Systematic investigations of the electric dipole (E1) modes of excitation are performed using the canonicalbasis time-dependent Hartree-Fock-Bogoliubov (Cb-TDHFB) theory. The Cb-TDHFB is able to describe dynamical pairing correlations in excited states of nuclear systems. We apply the method to the real-time calculation of linear response in even-even nuclei with Skyrme functionals. Effects of shell structure, neutron skin, deformation, and neutron chemical potential (separation energy) are studied in a systematic way. This reveals a number of characteristic features of the low-energy E1 modes. We also find a universal behavior in the low-energy E1 modes for heavy neutron-rich isotopes, which suggests the emergence of decoupled E1 peaks beyond N = 82.

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“…There are some calculations beyond the (Q)RPA as well [44][45][46][47][48][49]. However, even in the (Q)RPA level, different models often predict different properties.…”

Section: Introductionmentioning

confidence: 99%

Systematic investigation of low-lying dipole modes using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory

2014

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“…The SRPA explicitly incorporates the two-particle-two-hole (2p2h) states instead of "two-phonon" states, and respects the Pauli principle in the 2p2h configurations. Recently, the low-energy dipole states in 40,48 Ca have been studied with the SRPA [18], which suggests that the coupling between one-particle-one-hole (1p1h) and 2p2h configurations enhances the electric dipole (E1) strength in the energy range from 5 to 10 MeV. We investigate whether a similar effect can be observed in the isotones of N = 82.…”

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confidence: 95%

Fragmentation of electric dipole strength inN=82isotones

Tohyama

Nakatsukasa

2012

Phys. Rev. C

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Fragmentation of the dipole strength in the N = 82 isotones 140 Ce, 142 Nd and 144 Sm is calculated using the second random-phase approximation (SRPA). In comparison with the result of the random-phase approximation (RPA), the SRPA provides the additional damping of the giant dipole resonance and the redistribution of the low-energy dipole strength. Properties of the low-energy dipole states are significantly changed by the coupling to two-particle-two-hole (2p2h) states, which are also sensitive to the correlation among the 2p2h states. Comparison with available experimental data shows a reasonable agreement for the low-energy E1 strength distribution.PACS numbers: 21.60. Jz, 24.30.Cz, 27.60.+j The low-energy dipole states, often referred to as the pygmy dipole resonance (PDR), have attracted recent experimental [1][2][3][4][5][6] and theoretical interests [7][8][9][10][11][12] (see also the recent review [13] and references therein). It is also of significant astrophysical interest, since the low-energy dipole strengths close to the neutron threshold strongly affect the astrophysical r-process nucleosynthesis [14].The quasiparticle random-phase approximation based on the Hartree-Fock-Bogoliubov ground state (HFB+QRPA) has been extensively used to study the PDR as well as the giant dipole resonances (GDR). Recent systematic calculations [15] for the Nd and Sm isotopes show that although the HFB+QRPA nicely reproduces characteristic features of the shape phase transition in the GDR, it fails to produce the low-energy dipole strengths at E x = 5.5 ∼ 8 MeV, observed in the N = 82 isotones, 142 Nd and 144 Sm [1,3]. The disagreement suggests that the coupling to complex configurations, such as multi-particle-multi-hole states, are required to study the PDR in these nuclei. In fact, the quasiparticle-phonon model (QPM), which takes into account coupling to multi-phonon states, successfully reproduces the low-energy dipole strengths in the N = 82 nuclei [2,4]. A similar approach based on the relativistic mean-field model has also been used to study the PDR in the tin and nickel isotopes [16]. These models assume the multi-phonon characters of the complex states and violate the Pauli principle. Thus, it is desirable to study properties of the PDR with a method complementary to these phonon-coupling approaches. In this work, we present studies for the dipole excitations in the N = 82 isotones, with the second random-phase approximation (SRPA) (Ref.[17] and references therein). The SRPA explicitly incorporates the two-particle-two-hole (2p2h) states instead of "two-phonon" states, and respects the Pauli principle in the 2p2h configurations. Recently, the low-energy dipole states in 40,48 Ca have been studied with the SRPA [18], which suggests that the coupling between one-particle-one-hole (1p1h) and 2p2h configurations enhances the electric dipole (E1) strength in the energy range from 5 to 10 MeV. We investigate whether a similar effect can be observed in the isotones of N = 82. Since there are many dipole states w...

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“…With increasing the number of neutrons, a phenomenon called pygmy dipole resonance (PDR) is predicted in neutron-rich nuclei and a number of theoretical and experimental studies were devoted to its properties in the recent years [16][17][18][19][20][21][22][23]. The PDR has often been interpreted as a manifestation of the oscillation of the weakly-bound neutron skin against the isospin-symmetric core of protons and neutrons, although this picture is rather sketchy.…”

Section: Introductionmentioning

confidence: 99%

Effective restoration of dipole sum rules within the renormalized random-phase approximation

et al. 2016

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The dipole excitations for calcium and zirconium isotopes are studied within the fully selfconsistent Hartree-Fock mean field incorporated with the renormalized random-phase approximation (RRPA) using the Skyrme interaction SLy5. The RRPA takes into account the effect of ground-state correlations beyond RPA owing to the Pauli principle between the particle-hole pairs that form the RPA excitations as well as the correlations due to the particle-particle and hole-hole transitions, whose effects are treated here in an effective way. By comparing the RPA results with the RRPA ones, which are obtained for isoscalar (IS) and isovector (IV) dipole excitations in 48,52,58 Ca and 90,96,110 Zr, it is shown that ground-state correlations beyond the RPA reduce the IS transition strengths. They also shift up the energy of the lowest IV dipole state and slightly push down the peak energy of the IV giant dipole resonance. As the result, the energy-weighted sums of strengths of both IS and IV modes decrease, causing the violation of the corresponding energyweight sum rules (EWSR). It is shown that this sum rule violation can be eliminated by taking into account the contribution of the particle-particle and hole-hole excitations together with the particle-hole ones in a simple and perturbative way. Consequently, the ratio of the energy-weighted sum of strengths of the pygmy dipole resonance to that of the giant dipole resonance increases.

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Low-lying dipole response in the stable40,48Ca nuclei with the second random-phase approximation

Cited by 67 publications

References 56 publications

Systematic investigation of low-lying dipole modes using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory

Systematic investigation of low-lying dipole modes using the canonical-basis time-dependent Hartree-Fock-Bogoliubov theory

Fragmentation of electric dipole strength inN=82isotones

Effective restoration of dipole sum rules within the renormalized random-phase approximation

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