Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

Matsuo, Masayuki

doi:10.1103/physrevc.91.034604

Cited by 20 publications

(20 citation statements)

References 54 publications

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“…However, for open-shell and heavier systems, we need to simultaneously treat the deformation and the paring correlations. This has not been achieved yet, however, partially done with modern EDFs; the Green's function method for deformed systems (Nakatsukasa and Yabana, 2005) and that for superconducting systems (Daoutidis and Ring, 2011;Matsuo, 2015;Mizuyama et al, 2009;Serizawa and Matsuo, 2009).…”

Section: Nuclear Response In the Continuummentioning

confidence: 99%

“…It has been known that one can decompose the strength function (the photoabsorption cross section) in the continuum RPA into partial strength functions for individual channels of particle escape (Nakatsukasa and Yabana, 2001;Zangwill and Soven, 1980). Matsuo (2015) has recently extended the idea to the continuum QRPA. The decomposition allows, using the reciprocity theorem for the inverse processes, to compute the cross section of the direct neutron capture cross sections for different entrance channels separately.…”

Section: Nuclear Response In the Continuummentioning

confidence: 99%

“…Otherwise, spurious number-fluctuation modes would heavily mix in the LACM of interest. This can be achieved in the SCC method (Matsuo, 1986).…”

Section: Inclusion Of the Pair Rotation And Gauge Invariancementioning

confidence: 99%

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Time-dependent density-functional description of nuclear dynamics

et al. 2016

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We present the basic concepts and recent developments in the time-dependent density functional theory (TDDFT) for describing nuclear dynamics at low energy. The symmetry breaking is inherent in nuclear energy density functionals (EDFs), which provides a practical description of important correlations at the ground state. Properties of elementary modes of excitation are strongly influenced by the symmetry breaking and can be studied with TDDFT. In particular, a number of recent developments in the linear response calculation have demonstrated their usefulness in description of collective modes of excitation in nuclei. Unrestricted real-time calculations have also become available in recent years, with new developments for quantitative description of nuclear collision phenomena. There are, however, limitations in the real-time approach; for instance, it cannot describe the many-body quantum tunneling. Thus, we treat the quantum fluctuations associated with slow collective motions assuming that time evolution of densities are determined by a few collective coordinates and momenta. The concept of collective submanifold is introduced in the phase space associated with the TDDFT and used to quantize the collective dynamics. Selected applications are presented to demonstrate the usefulness and quality of the new approaches. Finally, conceptual differences between nuclear and electronic TDDFT are discussed, with some recent applications to studies of electron dynamics in the linear response and under a strong laser field.

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Section: Nuclear Response In the Continuummentioning

confidence: 99%

Section: Nuclear Response In the Continuummentioning

confidence: 99%

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Time-dependent density-functional description of nuclear dynamics

et al. 2016

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“…For the DC process, however, the exotic modes need to be described explicitly as a doorway state of the neutron capture, and also do gammadecays from the populated excited state. Such theoretical descriptions of the DC process, applicable to the medium and heavy neutron-rich nuclei (relevant to the r-process), have not been formulated, in our knowledge, except our preceding study [12]. The DC models applied so far to medium and heavy nuclei adopt the independent particle model [13][14][15][16][17][18], in which the collective effect is neglected.…”

Section: Introductionmentioning

confidence: 99%

Continuum random-phase approximation for gamma transition between excited states in neutron-rich nuclei

Saito,

Matsuo

2021

Preprint

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A characteristic feature of collective and particle-hole excitations in neutron-rich nuclei is that many of them couple to unbound neutron in continuum single-particle orbits. The continuum random phase approximation (cRPA) is a powerful many-body method that describes such excitations, and it provides a scheme to evaluate transition strengths from the ground state. In an attempt to apply cRPA to the radiative neutron capture reaction, we formulate in the present study an extended scheme of cRPA that describes gamma-transitions from the excited states under consideration, which decay to low-lying excited states as well as the ground state. This is achieved by introducing a non-local one-body operator which causes transitions to a low-lying excited state, and describing a density-matrix response against this operator. As a demonstration of this new scheme, we perform numerical calculation for dipole, quadrupole, and octupole excitations in 140 Sn, and discuss E1 and E2 transitions decaying to low-lying 2 + 1,2 and 3 − 1 states. The results point to cases where the branching ratio to the low-lying states is larger than or comparable with that to the ground state. We discuss key roles of collectivity and continuum orbits in both initial and final states.

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“…The second part of the question we have posed above is related to scattering in the particle continuum. In most theoretical studies so far the particle continuum is at best discretized (for recent exceptions see, e.g., [30,31]). Broad resonances in the vicinity of the particle threshold may not be adequately described.…”

Section: Introductionmentioning

confidence: 99%

Isoscalar and neutron modes in theE1spectra of Ni isotopes and the relevance of shell effects and the continuum

2015

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We study theoretically the electric dipole transitions of even Ni isotopes at low energies, using the self-consistent quasi-particle random-phase approximation with the D1S Gogny interaction and a continuum-RPA model with the SLy4 Skyrme force. We analyze isoscalar states, isovector states, and the dipole polarizability. We define a reference value for the polarizability, to remove a trivial dependence on the mass number. We compare our results with data and other calculations, with a focus on collective states, shell effects, and threshold transitions.Our results support the presence of a strong isoscalar transition, with little or moderate E1 strength, as a universal feature of ordinary nuclei. In moderately neutron-rich Ni isotopes, namely 68 Ni and neighboring isotopes, this transition is found bimodal due to couplings with surface neutrons. An adequate treatment of the continuum states appears essential for describing suprathreshold E1 strength, especially beyond 68 Ni. Very exotic isotopes (N > 50) are found highly polarizable, with practically all their E1 strength in the continuum. The dipole polarizability and the neutron-skin thickness are influenced by shell structure in different ways, so that they can appear anticorrelated. A comparison with existing results for lighter (Ca) and heavier (Sn) nuclei suggests that the so-called pygmy dipole strength is influenced strongly by shell effects and that, partly for that reason, its isospin structure depends on the mass region.

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Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

Abstract: We formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random phase approximation (QRPA). A focus is put on very neutron-rich nuclei and low-energy

Cited by 20 publications

References 54 publications

Time-dependent density-functional description of nuclear dynamics

Time-dependent density-functional description of nuclear dynamics

Continuum random-phase approximation for gamma transition between excited states in neutron-rich nuclei

Isoscalar and neutron modes in theE1spectra of Ni isotopes and the relevance of shell effects and the continuum

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