New perspectives on the level density of compound resonances

Rohr, G.

doi:10.1007/bf01418087

Cited by 57 publications

(40 citation statements)

References 10 publications

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“…The empty circles (red color) present the low energy fit, around 1-5 MeV, while the filled circles (black color) present the standard 5-25 MeV energy range fit. We can see that at low energies the fitted level density parameter a is slightly larger, but still it is not large enough to be compared with the empirical estimates [52,53]. …”

Section: Thermodynamic Description and Comparison With Phenomenolmentioning

confidence: 91%

“…This is the known Rosenzweig effect [54] described by Ericson [17] as due to "a considerably larger number of rearrangement possibilities when the shell is half-filled". The empirical estimates for the same nuclei are available from the level density at the neutron resonances energy [52], which do not show considerable shell effects, and by extrapolation from low-lying levels [53] where one can see very weak shell effects in the region of the mass number around A ≈ 50. The Constant in Eq.…”

Section: Thermodynamic Description and Comparison With Phenomenolmentioning

confidence: 99%

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Nuclear level density: Shell-model approach

Sen'kov

Zelevinsky

2016

Phys. Rev. C

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The knowledge of the nuclear level density is necessary for understanding various reactions including those in the stellar environment. Usually the combinatorics of Fermi-gas plus pairing is used for finding the level density. Recently a practical algorithm avoiding diagonalization of huge matrices was developed for calculating the density of many-body nuclear energy levels with certain quantum numbers for a full shell-model Hamiltonian. The underlying physics is that of quantum chaos and intrinsic thermalization in a closed system of interacting particles. We briefly explain this algorithm and, when possible, demonstrate the agreement of the results with those derived from exact diagonalization. The resulting level density is much smoother than that coming from the conventional mean-field combinatorics. We study the role of various components of residual interactions in the process of thermalization, stressing the influence of incoherent collision-like processes. The shell-model results for the traditionally used parameters are also compared with standard phenomenological approaches.

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Section: Thermodynamic Description and Comparison With Phenomenolmentioning

confidence: 91%

Section: Thermodynamic Description and Comparison With Phenomenolmentioning

confidence: 99%

Nuclear level density: Shell-model approach

Sen'kov

Zelevinsky

2016

Phys. Rev. C

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“…In addition to the von Egidy compilation, other compilations have been prepared by Rohr [22] and Al-Quraishi et al [23]. These parameters are shown in Table I.…”

Section: Level Density Of 56 Fementioning

confidence: 99%

Level density ofFe56and low-energy enhancement of γ-strength function

et al. 2006

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The 55 Mn(d, n) 56 Fe differential cross section is measured at E d = 7 MeV. The 56 Fe level density obtained from neutron evaporation spectra is compared to the level density extracted from the 57 Fe( 3 He,αγ) 56 Fe reaction by the Oslo-type technique. Good agreement is found between the level densities determined by the two methods. With the level density function obtained from the neutron evaporation spectra, the 56 Fe γ-strength function is also determined from the first-generation γ matrix of the Oslo experiment. The good agreement between the past and present results for the γ-strength function supports the validity of both methods and is consistent with the low-energy enhancement of the γ strength below ∼ 4 MeV first discovered by the Oslo method in iron and molybdenum isotopes.

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“…It is thus interesting to see how the emission of high-energy 7 rays will be modified. The value a=A/8 is commonly used in statistical model calculations since it reproduces the average behaviour observed near the neutron threshold [17,18]. However, even at such a low excitation energy strong deviations from the average value have been observed.…”

Section: Analysis and Discussionmentioning

confidence: 96%

Influence of the giant dipole resonance in the statistical decay of the compound nucleus160Er

Tobbeche

Barrette

Haas³

et al. 1986

Z. Physik A - Atomic Nuclei

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Evaporation residue excitation functions and statistical 7-ray spectra have been measured in the heavy ion fusion reaction ~60+144Nd~16~ between EL~b=76 and 105 MeV. In agreement with statistical model calculations, the evolution of the 7-ray spectra as a function of the compound nucleus excitation energy is consistent with the emission of high-energy ~ rays (E~> 10 MeV) in the early stage of the decay process. The description of the evaporation residue distributions by the statistical model is improved if a 7 strength function including a giant dipole resonance built on each excited state and describing the shape of the measured statistical 7-ray spectra is used in the calculations. The present analysis shows, however, that there is a strong correlation between the parameters of the resonance deduced from the fit to the 7-ray spectra and other parameters of the statistical model, in particular the level density parameter.

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New perspectives on the level density of compound resonances

Cited by 57 publications

References 10 publications

Nuclear level density: Shell-model approach

Nuclear level density: Shell-model approach

Level density ofFe56and low-energy enhancement of γ-strength function

Influence of the giant dipole resonance in the statistical decay of the compound nucleus160Er

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