Global investigation of the fine structure of the isoscalar giant quadrupole resonance

Shevchenko, A.; Burda, O.; Carter, J.; Cooper, G.R.J.; Fearick, R.; Förtsch, S. V.; Fujita, H.; Fujita, Y.; Kalmykov, Y.; Lacroix, Denis; Lawrie, J. J.; Neumann-Cosel, P. von; Neveling, R.; Ponomarev, V. Yu.; Richter, A.; Sideras‐Haddad, E.; Smit, F. D.; Wambach, J.

doi:10.1103/physrevc.79.044305

Cited by 32 publications

(70 citation statements)

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“…In the former Landau damping causes the pronounced structures observed in 208 Pb between about 9 and 12 MeV. For the latter resonance fine structure was shown [6,7] to arise from the contribution to the spreading width due to coupling to low-energy surface vibrations [9]. For the case of the IVGDR it is important to study the fine structure systematically over a wider mass range in order to clarify to what extent the dominant role of Landau damping is a general phenomenon or related to the doubly closed-shell structure of 208 Pb.…”

Section: Discussionmentioning

confidence: 94%

“…The consistency of characteristic scales extracted with and without 2p2h states indicates that the coupling of the 1p1h doorway states to more complex states is weak and suggests Landau damping as the main source of fine structure of the IVGDR in 208 Pb. Since no additional scales appear with the inclusion of complex configurations, other mechanisms like direct decay or the coupling to low-lying collective vibrations identified as dominant mechanism inducing fine structure in ISGQR in heavy nuclei [7] seem to play a minor role only.…”

Section: Discussionmentioning

confidence: 99%

“…The similarity between the power spectra and scales deduced from the QPM calculation for a one-phonon model space with those including two-phonon states suggests that the fragmentation of 1p1h transitions (i.e., Landau damping) is the most important mechanism leading to fine structure of the IVGDR in 208 Pb. The coupling to complex configurations and, in particular, to low-lying collective vibrations identified as dominant mechanism in the ISGQR in heavy nuclei [7] seems to play a minor role only. While the relative weight changes, major scales are also found at about the same energies in the CWT analysis of the RRPA (d) and RTBA (e) results.…”

Section: B Application To the Ivgdr In 208 Pbmentioning

confidence: 99%

“…Applications of the CWT to high-resolution nuclear spectra of giant resonances are described in Refs. [6,7,10,30]. Further details and a comparison with other techniques for the analysis of fine structure in nuclear giant resonances can be found in Ref.…”

Section: A Continuous Wavelet Transform (Cwt)mentioning

confidence: 99%

“…For comparable energy resolution, the fine structure is independent of the exciting probe [5]. A case study of this method has been performed for the isoscalar giant qudrupole resonance (ISGQR) from medium-mass to heavy nuclei [6,7]. Different approaches for an extraction of energy scales characterizing the observed fine structure have been compared in Ref.…”

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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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Section: B Application To the Ivgdr In 208 Pbmentioning

confidence: 99%