Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes

Arsenyev, N. N.; Severyukhin, A. P.; Voronov, V. V.; Giai, Nguyen Van

doi:10.1051/epjconf/201819404002

Cited by 2 publications

(2 citation statements)

References 29 publications

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“…To compare the magnitudes of the matrix elements corresponding to projected and unprojected states, we consider the case of a Nilsson Ω state that extends over the spherical shell model basis: Because the state norms are larger than unity and the remaining two factors are close to unity, it can be said that the rotations affect the E1 matrix elements by increasing them. Several self-consistent approaches based on realistic two-body interactions and using a Hartree-Fock plus QRPA [16,17,21,22] or relativistic functional density formalism [26,67] have been proposed to describe similar issues, as in this study. The current approach has the advantage of simplicity, although a lack of self-consistency may be considered a weak point.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, isoscalar dipole strength distribution was studied using a self-consistent random-phase approximation (RPA) approach [16]. In addition, in [17], starting with the Skyrme mean-field calculation, some properties of the electric dipole strength in Ca isotopes were studied by taking into account the coupling of one-and two-phonon terms in the wavefunctions of the excited states. An alternative way to treat effects, such as resonance shift and collisional damping, caused by going beyond the RPA approach is to use a second random-phase approximation (SRPA) to treat the 2p2h interaction [18].…”

Section: Introductionmentioning

confidence: 99%

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Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm

Raduta,

Raduta

2024

J. Phys. G: Nucl. Part. Phys.

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A many body Hamiltonian consisting in a spherical shell model mean field term, a pairing interaction for alike nucleons and a dipole-dipole interaction, with the dipole operator involving a cubic term in the radial coordinate, is studied within a quasiparticle random phase approximation (QRPA) and applied numerically to five even-even isotopes of Sm. The resulting wave functions are further used to calculate the B(E1) values which at their turn are employed to calculate the photo absorption cross section, the integrated moments of the cross section and the energy weighted sum rule (EWSR). The calculated cross section and its integrated moments are compared with the available data and a good agreement is pointed out. One distinguishes two regionscorresponding to the Pygmy Dipole Resonance (PDR), 1-10 MeV, and to the Giant Dipole Resonance (GDR), 10-20 MeV respectively, these being separately studied. The peaks belonging to each of the two ranges are in detail analyzed. The PDR states are located around the neutron separation energy and are mainly formed of collective isoscalar and neutron collective states. The PDR states describe oscillations of the neutrons excess against the protons from the isospin saturated core. The character of the states from the GDR region, isoscalar or isovector, is also pointed out. The PDR states carry only 0.8-2.7$\%$ of the total EWSR and 0.4-5.9$\%$ of the total E1 strength. The dependence of the dipole strength on nuclear deformation is evidenced. A comment on the cross section split into two branches for deformed isotopes, is included. The r-cubic term and the nuclear deformation have opposite effect on the dipole strength. Also it diminishes the effect of the non-conservation of the center of mass momentum. The famous Thomas Reiche Kuhn sum rule formula is generalized to the case of the Schiff dipole momentum. The new sum rule is well satisfied. The projected spherical single particle basis used in our formalism allows for an unified description of the spherical transitional and deformed isotopes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm

Raduta,

Raduta

2024

J. Phys. G: Nucl. Part. Phys.

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Microscopic description of the pygmy and giant dipole resonances in even–even nuclei. Application to the isotopes 150,152,154,156,158,160Gd

Raduta,

Poenaru

2024

Int. J. Mod. Phys. E

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This paper deals with a microscopic approach for the description of the pygmy dipole resonance (PDR) as well as of the giant dipole resonance (GDR). The formalism is based on a Hamiltonian which is summing a mean field term, the pairing for alike nucleons and the dipole–dipole interaction. Two features are specific for our description: (a) The use of a projected spherical single particle basis and (b) the involved dipole operator is a Schif-like operator including a corrective term which is cubic in the radial coordinate. The dipole strength distribution with energy is plotted for the PDR region, i.e., [0,10] MeV. The dominant transitions have an isovector character for three isotopes and isoscalar for another three. The PDR states carry only 0.4–1.8[Formula: see text] of the total EWSR. The dependence of the dipole strength on nuclear deformation is evidenced. For the whole interval of [0,20] MeV the dipole strength was first folded by Lorentzian of 1[Formula: see text]MeV width and then plotted as function of the QRPA energies. The peaks belonging to each of the two ranges are analyzed in detail and their nature, isovector/isoscalar, was pointed out. The r-cubic term and the nuclear deformation have opposite effects on the dipole strength. The famous Thomas–Reiche–Kuhn sum rule formula is generalized to the case of the Schiff dipole momentum. The new EWSR is very well satisfied. The photoabsorbtion cross-section is calculated and compared with experimental data in a figure showing its dependence on energy. The total cross-section, [Formula: see text], the moments of the integrated cross-sections, [Formula: see text], [Formula: see text], the dipole polarizability and the thickness of the neutron crust are also calculated. The main features of PDR and GDR are realistically described.

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Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes

Cited by 2 publications

References 29 publications

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm

Microscopic description of the pygmy and giant dipole resonances in even–even nuclei. Application to the isotopes 150,152,154,156,158,160Gd

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Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes

Cited by 2 publications

References 29 publications

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes 144,148,150,152,154Sm

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes 144,148,150,152,154Sm

Microscopic description of the pygmy and giant dipole resonances in even–even nuclei. Application to the isotopes 150,152,154,156,158,160Gd

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Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm

Toward a new approach for the pygmy dipole resonance in even–even nuclei. Application to isotopes ^{144,148,150,152,154}Sm