Analysis of fine structure in the nuclear continuum

Shevchenko, A.; Carter, J.; Cooper, G.R.J.; Fearick, R.; Kalmykov, Y.; Neumann-Cosel, P. von; Ponomarev, V. Yu.; Richter, A.; Usman, I. T.; Wambach, J.

doi:10.1103/physrevc.77.024302

Cited by 37 publications

(58 citation statements)

References 25 publications

(46 reference statements)

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“…9 in Ref. [8]). It also provides another useful property which can be applied for a determination of background in the data.…”

Section: B Background Determinationmentioning

confidence: 99%

“…Further details and a comparison with other techniques for the analysis of fine structure in nuclear giant resonances can be found in Ref. [8].…”

Section: A Continuous Wavelet Transform (Cwt)mentioning

confidence: 99%

“…A DWT can only be performed with wavelets which possess a so-called scaling function [8]. This is not the case for the Morlet wavelet, thus the Bior3.9 wavelet function is used as an alternative.…”

Section: B Background Determinationmentioning

confidence: 99%

“…9 in Ref. [8]) because the detector response is typically close to the Gaussian line shape and the Morlet wavelet is a product of Gaussian and cosine functions…”

Section: A Continuous Wavelet Transform (Cwt)mentioning

confidence: 99%

“…Different approaches for an extraction of energy scales characterizing the observed fine structure have been compared in Ref. [8]. Wavelet analysis has been identified as a particularly promising type of analysis.…”

Section: Introductionmentioning

confidence: 99%

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Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

et al. 2014

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Background: The electric isovector giant dipole resonance (IVGDR) in208 Pb has been measured with high energy resolution with the (p, p ) reaction under extreme forward angles [A. Tamii et al., Phys. Rev. Lett. 107, 062502 (2011)] and shows considerable fine structure.Purpose: The aim of the present work is to extract scales characterizing the observed fine structure and to relate them to dominant decay mechanisms of giant resonances. Furthermore, the level density of J π = 1 − states is determined in the energy region of the IVGDR.Methods: Characteristic scales are extracted from the spectra with a wavelet analysis based on continuous wavelet transforms.Comparison with corresponding analyses of B(E1) strength distributions from microscopic model calculations in the framework of the quasiparticle phonon model and the relativistic random phase approximation allow to identify giant resonance decay mechanisms responsible for the fine structure. The level density of 1 − states is related to local fluctuations of the cross sections in the energy region of the IVGDR, where contributions from states with other spin-parities can be neglected. The magnitude of the fluctuations is determined by the autocorrelation function.Results: Scales in the fine structure of the IVGDR in 208 Pb are found at 80, 130, 220, 430, 640, 960 keV, and at 1.75 MeV. The values of the most prominent scales can be reasonably well reproduced by the microscopic calculations although they generally yield a smaller number of scales.. The inclusion of complex configurations in the calculations changes the E1 strength distributions but the impact on the wavelet power spectra and characteristic scales is limited. The level density of 1 − states is extracted in the excitation energy range 9 − 12.5 MeV and compared to a variety of phenomenological and microscopic models. Conclusions:In both models the major scales are already present at the one-particle one-hole level indicating Landau damping as a dominant mechanism responsible for the fine structure of the IVGDR in contrast to the isoscalar giant quadrupole resonance, where fine structure arises from the coupling to low-lying surface vibrations. The back-shifted Fermi gas model parameterization of Rauscher et al., Phys. Rev. C 56, 1613 describes the level-density data well, while other phenomeological and microscopic approaches fail to reproduce absolute values or the energy dependence or both.

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“…9 in Ref. [8]). It also provides another useful property which can be applied for a determination of background in the data.…”

Section: B Background Determinationmentioning

confidence: 99%

“…Further details and a comparison with other techniques for the analysis of fine structure in nuclear giant resonances can be found in Ref. [8].…”

Section: A Continuous Wavelet Transform (Cwt)mentioning

confidence: 99%

Section: B Background Determinationmentioning

confidence: 99%

“…9 in Ref. [8]) because the detector response is typically close to the Gaussian line shape and the Morlet wavelet is a product of Gaussian and cosine functions…”

Section: A Continuous Wavelet Transform (Cwt)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

et al. 2014

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High Energy-Resolution Experiments with the K600 Magnetic Spectrometer at Intermediate Energies

Usman

2013

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2013

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Before the thorough discussions on each particular case, we first present our principal idea. It is often quite reasonable to start with the microscopic calculation of self-consistent mean-field (potential) energy surface with energy density functional (EDF), from which collective spectra and transition rates are derived (cf. Fig. 2.1). Since the energy surface reflects intrinsic deformation, the question arises here: How can we incorporate the energy-surface calculation into the relevant measurable spectroscopic properties with good symmetries? There have been many EDF-based schemes which derive spectroscopic properties from the energy surface, including the generator coordinate method (GCM), collective Hamiltonian approach, etc. 1 These studies are, however, still computationally quite complicated and demanding. Our motivation to employ the interacting boson model (IBM) is twofold: First, IBM can be utilized as an effective theory to generate excitation energies and transition rates with good symmetries in a computationally much moderate way, in comparison to other mean-field based, spectra-generating approaches mentioned above. The second is rather profound. Formulating the IBM by EDF approach should be of certain interest because it may help clarifying the major long-lasting problem of IBM concerning its microscopic foundation.Note that this chapter is not intended to the complete review of the mean-field theory and the IBM. For pedagogical literature of these two models, the interested reader is referred to the textbook by Ring

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Analysis of fine structure in the nuclear continuum

Cited by 37 publications

References 25 publications

Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

Fine structure of the isovector giant dipole resonance inPb208: Characteristic scales and level densities

High Energy-Resolution Experiments with the K600 Magnetic Spectrometer at Intermediate Energies

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