Extended theory of finite Fermi systems: collective vibrations in closed shell nuclei

Kamerdzhiev, S.; Speth, J.; Tertychny, G.

doi:10.1016/j.physrep.2003.11.001

Cited by 173 publications

(219 citation statements)

References 123 publications

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“…[24]. On the non-relativistic side, such techniques have also been used in the context of the non-spectral representation without [62,63] and with [64] pairing. So far, however, fully self-consistent relativistic applications including complex configurations with a proper treatment of the continuum are still missing.…”

Section: Discussionmentioning

confidence: 99%

Continuum random-phase approximation for relativistic point coupling models

Daoutidis

Ring

2009

Phys. Rev. C

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Relativistic Continuum Random Phase Approximation (CRPA) is used to investigate collective excitation phenomena in several spherical nuclei along the periodic table. We start from relativistic mean field calculations based on a covariant density functional with density dependent zero range forces. From the same functional an effective interaction is obtained as the second derivative with respect to the density. This interaction is used in relativistic continuum-RPA calculations for the investigation of isoscalar monopole, isovector dipole and isoscalar quadrupole resonances of spherical nuclei. In particular we study the low-lying E1 strength in the vicinity of the neutron evaporation threshold. The properties of the resonances, such as centroid energies and strengths distributions are compared with results of discrete RPA calculations for the same model as well as with experimental data.

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Section: Discussionmentioning

confidence: 99%

Continuum random-phase approximation for relativistic point coupling models

Daoutidis

Ring

2009

Phys. Rev. C

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“…In general, the ETFFS(QTBA) accounts for the singleparticle continuum completely at the RPA level for magic nuclei and includes the new effect of ground-state correlations caused by PC [3]. However, because of the technical difficulties connected with pairing, these effects are not considered in the present calculations.…”

Section: A Methodsmentioning

confidence: 99%

“…In particular, PC explains approximately 50% of the observed width, its gross structure, and sometimes some fine structure (e.g., for the E2 isoscalar resonance in 208 Pb [3]). However, the direct influence of PC on the giant resonance of unstable nuclei has been much less studied, although it is expected to be as important as it is for stable nuclei.…”

Section: Introductionmentioning

confidence: 99%

“…Here the most realistic approaches include complex configurations with phonons; namely, the coupling of single-particle degrees of freedom with the phonon degrees (the so-called phonon coupling or PC). These approaches are referred to in the literature as the quasiparticle-phonon model [1], the (Q)RPA + phononcoupling model [(Q)RPA + PC] [2] and the extended theory of finite Fermi systems (ETFFS) [3]. The latter is based on the Green function method and includes the single-particle continuum which is necessary for nuclei with a nucleon separation energy close to zero.…”

Section: Introductionmentioning

confidence: 99%

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Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Авдеенков

Goriely²,

Kamerdzhiev

et al. 2011

Phys. Rev. C

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The E1 strength function for 15 stable and unstable Sn even-even isotopes from A = 100 to A = 176 are calculated using a self-consistent microscopic theory which, in addition to the standard (quasiparticle) randomphase approximation [(Q)RPA] approach, takes into account phonon coupling and the single-particle continuum (by means of the discretization procedure) with a cutoff of 100 MeV. Our analysis shows two distinct regions for which the integral characteristics of both the giant and pygmy resonances behave rather differently. For neutron-rich nuclei, starting from 132 Sn, we obtain a giant E1 resonance which significantly deviates from the widely used systematics extrapolated from experimental data in the β-stability valley. We show that the inclusion of phonon coupling is necessary for a proper description of the low-energy pygmy resonances and the corresponding transition densities for A < 132 nuclei, while in the A > 132 region the influence of phonon coupling is significantly smaller. The radiative neutron capture cross sections leading to the stable 124 Sn and unstable 132 Sn and 150 Sn nuclei are calculated with both the (Q)RPA and the beyond-(Q)RPA strength functions and shown to be sensitive to both the predicted low-lying strength and the phonon-coupling contribution. The comparison with the widely used phenomenological generalized Lorentzian approach shows considerable differences both for the strength function and the radiative neutron capture cross section. In particular, for the neutron-rich 150 Sn, the reaction cross section is found to be increased by a factor greater than 20. We conclude that the present approach may provide a complete and coherent description of the γ -ray-strength function for astrophysics applications. In particular, such calculations are highly recommended for a reliable estimate of the electromagnetic properties of exotic nuclei.

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“…In this work, we have applied for PSF the selfconsistent version of microscopic extended theory of finite Fermi systems (ETFFS) [4] in the time blocking approximation (TBA) [5]. For NLD, we used the phenomenological GSM [1], the EMPIRE specific NLD model [6] and the microscopic HFB plus combinatorial NLD model [7].…”

Section: Introductionmentioning

confidence: 99%

Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

Achakovskiy

Kamerdzhiev

Tselyaev

et al. 2016

EPJ Web of Conferences

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Abstract. The neutron capture cross sections and average radiative widths Γ γ of neutron resonances for two double-magic nuclei 132 Sn and 208 Pb have been calculated using the microscopic photon strength functions (PSF), which were obtained within the microscopic self-consistent version of the extended theory of finite Fermi systems in the time blocking approximation. For the first time, the microscopic PSFs have been obtained within the fully self-consistent approach with exact accounting for the single particle continuum (for 208 Pb). The approach includes phonon coupling effects in addition to the standard RPA approach. The known Skyrme force has been used. The calculations of nuclear reaction characteristics have been performed with the EM-PIRE 3.1 nuclear reaction code. Here, three nuclear level density (NLD) models have been used: the so-called phenomenological GSM, the EMPIRE specific (or Enhanced GSM) and the microscopical combinatorial HFB NLD models. For both considered characteristics we found a significant disagreement between the results obtained with the GSM and HFB NLD models. For 208 Pb, a reasonable agreement has been found with systematics for the Γ γ values with HFB NLD and with the experimental data for the HFB NLD average resonance spacing D 0 , while for these two quantities the differences between the values obtained with GSM and HFB NLD are of several orders of magnitude. The discrepancies between the results with the phenomenological EGLO PSF and microscopic RPA or TBA are much less for the same NLD model.

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Extended theory of finite Fermi systems: collective vibrations in closed shell nuclei

Cited by 173 publications

References 123 publications

Continuum random-phase approximation for relativistic point coupling models

Continuum random-phase approximation for relativistic point coupling models

Self-consistent calculations of the strength function and radiative neutron capture cross section for stable and unstable tin isotopes

Microscopic calculations of the characteristics of radiative nuclear reactions for double-magic nuclei

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