Nuclear resonance fluorescence experiments on 204,206,207,208Pb up to 6.75 MeV

Enders, J.; Brentano, P. von; Eberth, J.; Fitzler, A.; Fransen, C.; Herzberg, R.‐D.; Kaiser, H.; Käubler, L.; Neumann-Cosel, P. von; Pietralla, N.; Ponomarev, V. Yu.; Richter, A.; Schwengner, R.; Wiedenhöver, I.

doi:10.1016/s0375-9474(03)01554-9

Cited by 88 publications

(59 citation statements)

References 78 publications

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“…The low-energy dipole states have been observed in a number of nuclei: neutron-rich O isotopes [1,2], 26 Ne [3], stable Ca isotopes [4,5], 56 Fe and 58 Ni [6], 68 Ni [7], 88 Sr [8], 90 Zr [9,10], Sn isotopes [11][12][13][14][15], N = 82 isotones [16][17][18][19][20][21], and stable Pb isotopes [22][23][24][25][26]. The observed low-energy E1 strength exhausts less than 1% of the Thomas-Reiche-Kuhn (TRK) sum-rule value in stable isotopes, while it may amount up to about 5% in neutron-rich nuclei.…”

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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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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“…208 Pb has always been a benchmark and the PDR has been studied in various recent (γ, γ ′ ) experiments [14][15][16][17]. Theoretically, closed-shell nuclei permit the inclusion of complex degrees of freedom beyond the mean-field level in the microscopic calculations [14,18].…”

Section: The Heaviest Stable Doubly Magic Nucleusmentioning

confidence: 99%

Pygmy dipole resonance in208Pb

et al. 2012

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Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208 Pb shows that at very forward angles J π = 1 − states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(E1) transition strength distribution is extracted for excitation energies up to 9 MeV, i.e., in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to the underlying structure of the E1 transitions, which allows for the first time an experimental extraction of the electromagnetic transition strength and the energy centroid of the PDR.

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“…The remaining redundant N r − N n coefficients are undetermined and, therefore, can be safely put equal to zero. The eigenvalue problem within the n-phonon subspace is thereby solved exactly and yields a basis of orthonormal correlated n-phonon states of the form (8).…”

Section: Brief Description Of the Methodsmentioning

confidence: 99%

“…Radioactive beam experiments have extracted an appreciable dipole strength just above the neutron decay threshold in unstable nuclei, like neutron rich oxygen [3] or tin isotopes around 132 Sn [4]. More detailed data were obtained for stable nuclei by combining (γ, γ ′ ) [5][6][7][8][9][10][11][12][13][14] with (α, α ′ γ) measurements [15][16][17][18] which have detected rich low lying spectra of weakly excited discrete levels below the neutron threshold over different mass regions.…”

Section: Introductionmentioning

confidence: 99%

Dipole response inPb208within a self-consistent multiphonon approach

et al. 2015

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Background: The electric dipole strength detected around the particle threshold and commonly associated to the pygmy dipole resonance offers a unique information on neutron skin and symmetry energy, and is of astrophysical interest. The nature of such a resonance is still under debate.Purpose: We intend to describe the giant and pygmy resonances in 208 Pb by enhancing their fragmentation with respect to the random-phase approximation. Method:We adopt the equation of motion phonon method to perform a fully self-consistent calculation in a space spanned by one-phonon and two-phonon basis states using an optimized chiral two-body potential. A phenomenological density dependent term, derived from a contact three-body force, is added in order to get single-particle spectra more realistic than the ones obtained by using the chiral potential only. The calculation takes into full account the Pauli principle and is free of spurious center of mass admixtures. Results:We obtain a fair description of the giant resonance and obtain a dense low-lying spectrum in qualitative agreement with the experimental data. The transition densities as well as the phonon and particle-hole composition of the most strongly excited states support the pygmy nature of the low-lying resonance. Finally, we obtain realistic values for the dipole polarizability and the neutron skin radius. Conclusions:The results emphasize the role of the two-phonon states in enhancing the fragmentation of the strength in the giant resonance region and at low energy, consistently with experiments. For a more detailed agreement with the data, the calculation suggests the inclusion of the three-phonon states as well as a fine tuning of the single-particle spectrum to be obtained by a refinement of the nuclear potential.

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Nuclear resonance fluorescence experiments on 204,206,207,208Pb up to 6.75 MeV

Cited by 88 publications

References 78 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

Pygmy dipole resonance in208Pb

Dipole response inPb208within a self-consistent multiphonon approach

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