Spin- and Parity-Resolved Level Densities from the Fine Structure of Giant Resonances

Kalmykov, Y.; Özen, C.; Langanke, K.; Martı́nez-Pinedo, G.; Neumann-Cosel, P. von; Richter, A.

doi:10.1103/physrevlett.99.202502

Cited by 53 publications

(94 citation statements)

References 28 publications

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“…10 with the spin-and parity-dependent level density data extracted from Refs. [26,27]. In this figure, the raw NLDs (blue dotted line) as well as the normalized ones (full red line) are plotted.…”

Section: Resultsmentioning

confidence: 99%

Temperature-dependent combinatorial level densities with the D1M Gogny force

et al. 2012

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The combinatorial model of nuclear level densities has now reached a level of accuracy comparable to that of the best global analytical expressions without suffering from the limits imposed by the statistical hypothesis on which the latter expressions rely. In particular, it provides naturally, non-Gaussian spin distribution as well as nonequipartition of parities which are known to have a significant impact on cross section predictions at low energies. Our previous global model [S. Goriely, S. Hilaire, and A. J. Koning, Phys. Rev. C 78, 064307 (2008)] suffered from deficiencies, in particular in the way the collective effects-both vibrational and rotational-were treated. We have recently improved the level density calculations using simultaneously the single-particle levels and collective properties predicted by a newly derived Gogny interaction [S. Goriely, S. Hilaire, M. Girod, and S. Péru, Phys. Rev. Lett. 102, 242501 (2009)], therefore enabling a microscopic description of energy-dependent shell, pairing, and deformation effects. In addition, for deformed nuclei, the transition to sphericity is coherently taken into account on the basis of a temperature-dependent Hartree-Fock calculation which provides at each temperature the structure properties needed to build the level densities. This new method is described and shown to give reasonable results with respect to available experimental data.

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Section: Resultsmentioning

confidence: 99%

Temperature-dependent combinatorial level densities with the D1M Gogny force

et al. 2012

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“…These measurements [30][31][32] are obviously of great value in comparing with microscopic level density calculations even without the σ values.…”

Section: Applicationsmentioning

confidence: 99%

“…On the other hand, since the measured densities are for low J the total level density derived from resonance measurement will be increased. Finally, the new form does not have < J Some recent measurements [30,31] have deduced the level density for a specific spin and parity at a given excitation energy for specific nuclei. These measurements are analogous to neutron s-wave resonance measurements.…”

Section: Applicationsmentioning

confidence: 99%

Mass-number and excitation-energy dependence of the spin cutoff parameter

2016

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The spin cutoff parameter determining the nuclear level density spin distribution ρ(J) is defined through the spin projection as < J 2 z > 1/2 or equivalently for spherical nuclei, (It is needed to divide the total level density into levels as a function of J. To obtain the total level density at the neutron binding energy from the s-wave resonance count, the spin cutoff parameter is also needed. The spin cutoff parameter has been calculated as a function of excitation energy and mass with a super-conducting hamiltonian. Calculations have been compared with two commonly used semi-empirical formulas. A need for further measurements is also observed. Some complications for deformed nuclei are discussed. The quality of spin cut off parameter data derived from isomeric ratio measurement is examined.

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“…The extended analysis of the 90 Zr( 3 He,t) 90 Nb reaction in Ref. [25] indicates however fluctuations of the level density of 1 + states in 90 Nb around the predictions of the BSFG model.…”

Section: Determination Of the Dipole-strength Distributionmentioning

confidence: 99%

Pygmy dipole strength inZr90

et al. 2008

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The dipole response of the N = 50 nucleus 90 Zr was studied in photon-scattering experiments at the electron linear accelerator ELBE with bremsstrahlung produced at kinetic electron energies of 7.9, 9.0, and 13.2 MeV. We identified 189 levels up to an excitation energy of 12.9 MeV. Statistical methods were applied to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. In this way we derived the photoabsorption cross section up to the neutron-separation energy. This cross section matches well the photoabsorption cross section obtained from (γ, n) data and thus provides information about the extension of the dipole-strength distribution toward energies below the neutron-separation energy. An enhancement of E1 strength has been found in the range of 6 MeV to 11 MeV. Calculations within the framework of the quasiparticle-phonon model ascribe this strength to a vibration of the excessive neutrons against the N = Z neutron-proton core, giving rise to a pygmy dipole resonance.

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Spin- and Parity-Resolved Level Densities from the Fine Structure of Giant Resonances

Cited by 53 publications

References 28 publications

Temperature-dependent combinatorial level densities with the D1M Gogny force

Temperature-dependent combinatorial level densities with the D1M Gogny force

Mass-number and excitation-energy dependence of the spin cutoff parameter

Pygmy dipole strength inZr90

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