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A. V. Afanasjev

Publications and source records attributed to A. V. Afanasjev.

106 records · Page 6Linked to original sources

Cranked Relativistic Hartree-Bogoliubov Theory: probing the gateway to superheavy nuclei

The cranked relativistic Hartree+Bogoliubov theory has been applied for a systematic study of the nuclei around 254No, the heaviest elements for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasi-particle and other properties of these nuclei have been studied with different parametrizations for the effective mean-field Lagrangian. Pairing correlations are taken into account by a finite range two-body force of Gogny type. While the deformation properties are well reproduced, the calculations reveal some deficiencies of the effective forces both in the particle-hole and particle-particle channels. For the first time, the quasi-particle spectra of odd deformed nuclei have been calculated in a fully self-consistent way within the framework of the relativistic mean field (RMF) theory. The energies of the spherical subshells, from which active deformed states of these nuclei emerge, are described with an accuracy better than 0.5 MeV for most of the subshells with the NL1 and NL3 parametrizations. However, for a few subshells the discrepancies reach 0.7-1.0 MeV. In very heavy systems, where the level density is high, this level of accuracy is not sufficient for reliable predictions of the location of relatively small deformed shell gaps. The calculated moments of inertia reveal only small sensitivity to the RMF parametrization and, thus, to differences in the single-particle structure. However, in contrast to lighter systems, it is necessary to decrease the strength of the D1S Gogny force in the pairing channel in order to reproduce the moments of inertia.

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Global Lifetime Measurements of Highly-Deformed and Other Rotational Structures in the A~135 Light Rare-Earth Region: Probing the Single-Particle Motion in a Rotating Potential

It has been possible, using GAMMASPHERE plus Microball,to extract differential lifetime measurements free from common systematic errors for over 15 different nuclei (various isotopes of Ce, Pr, Nd, Pm, and Sm) at high spin within a single experiment. This comprehensive study establishes the effective single-particle quadrupole moments in the A~135 light rare-earth region. Detailed comparisons are made with calculations using the self-consistent cranked mean-field theory.

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Moments of Inertia of Nuclei in the Rare Earth Region: A Relativistic versus Non-Relativistic Investigation

A parameter free investigation of the moments of inertia of ground state rotational bands in well deformed rare-earth nuclei is carried out using Cranked Relativistic Hartree-Bogoliubov (CRHB) and non-relativistic Cranked Hartree-Fock-Bogoliubov (CHFB) theories. In CRHB theory, the relativistic fields are determined by the non-linear Lagrangian with the NL1 force and the pairing interaction by the central part of finite range Gogny D1S force. In CHFB theory, the properties in particle-hole and particle-particle channels are defined solely by Gogny D1S forces. Using an approximate particle number projection before variation by means of the Lipkin Nogami method improves the agreement with the experimental data, especially in CRHB theory. The effect of the particle number projection on the moments of inertia and pairing energies is larger in relativistic than in non-relativistic theory.

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Cranked relativistic Hartree-Bogoliubov theory: Superdeformation in the $A\sim 190$ mass region

A systematic investigation of the yrast superdeformed (SD) rotational bands in even-even nuclei of the $A\sim 190$ mass region has been performed within the framework of the cranked relativistic Hartree-Bogoliubov theory. The particle-hole channel of this theory is treated fully relativistically, while a finite range two-body force of Gogny type is used in the particle-particle (pairing) channel. Using the well established parameter sets NL1 for the Lagrangian and D1S for the Gogny force, very good description of experimental data is obtained with no adjustable parameters.

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Mean field studies of high-spin properties in the $A\sim 30$ and 60 regions of superdeformation

The importance of deformation changes and the possible role of proton-neutron pairing correlations on the properties of paired band crossings at superdeformation in the $A\sim 60$ mass region have been analyzed. The present analysis, supported in part by the cranked relativistic Hartree-Bogoliubov calculations for the SD band in $^{60}$Zn, suggests that when going from $^{60}$Zn to neighboring odd nuclei the properties of paired band crossings are strongly influenced by deformation changes. A number of questions related to the superdeformation in the $A\sim 30$ mass region has been studied with the cranked relativistic mean field theory and the configuration-dependent cranked Nilsson-Strutinsky approach.

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Time-odd mean fields in the rotating frame: microscopic nature of nuclear magnetism

The microscopic role of nuclear magnetism in rotating frame is investigated for the first time in the framework of the cranked relativistic mean field theory. It is shown that nuclear magnetism modifies the expectation values of single-particle spin, orbital and total angular momenta along the rotational axis effectively creating additional angular momentum. This effect leads to the increase of kinematic and dynamic moments of inertia at given rotational frequency and has an impact on effective alignments.

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Cranked Relativistic Hartree-Bogoliubov Theory: Formalism and Application to the Superdeformed Bands in the $A\sim 190$ region

Cranked Relativistic Hartree-Bogoliubov theory without and with approximate particle number projection by means of the Lipkin-Nogami method is presented in detail as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type. The applicability of this theory to the description of rotating nuclei is studied in detail on the example of superdeformed bands in even-even nuclei of the $A\sim 190$ mass region. Different aspects such as the importance of pairing and particle number projection, the dependence of the results on the parametrization of the RMF Lagrangian and Gogny force etc. are investigated in detail. It is shown that without any adjustment of new parameters the best description of experimental data is obtained by using the well established parameter sets NL1 for the Lagrangian and D1S for the pairing force. Contrary to previous studies at spin zero it is found that the increase of the strength of the Gogny force is not necessary in the framework of Relativistic Hartree-Bogoliubov theory provided that particle number projection is performed.

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Superdeformations in Relativistic and Non-Relativistic Mean Field Theories

The applications of the extensions of relativistic mean field (RMF) theory to the rotating frame, such as cranked relativistic mean field (CRMF) theory and cranked relativistic Hartree-Bogoliubov (CRHB) theory, for the description of superdeformed bands in the $A\sim 60$, 140-150 and 190 mass regions are overviewed and compared briefly with the results obtained in non-relativistic mean field theories.

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Cranked Relativistic Hartree-Bogoliubov Theory: Superdeformed Bands in the $A\sim 190$ Region

Cranked Relativistic Hartree-Bogoliubov (CRHB) theory is presented as an extension of Relativistic Mean Field theory with pairing correlations to the rotating frame. Pairing correlations are taken into account by a finite range two-body force of Gogny type and approximate particle number projection is performed by Lipkin-Nogami method. This theory is applied to the description of yrast superdeformed rotational bands observed in even-even nuclei of the $A\sim 190$ mass region. Using the well established parameter sets NL1 for the Lagrangian and D1S for the pairing force one obtains a very successful description of data such as kinematic ($J^{(1)}$) and dynamic ($J^{(2)}$) moments of inertia without any adjustment of new parameters. Within the present experimental accuracy the calculated transition quadrupole moments $Q_t$ agree reasonably well with the observed data.

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Rotating nuclei at extreme conditions: Cranked Relativistic Mean Field Description

The cranked relativistic mean field (CRMF) theory is applied for the description of superdeformed (SD) rotational bands observed in $^{153}$Ho. The question of the structure of the so-called SD band in $^{154}$Er is also addressed and a brief overview of applications of CRMF theory to the description of rotating nuclei at extreme conditions is presented.

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A comparative study of super- and highly-deformed bands in the A ~ 60 mass region

Super- and highly-deformed rotational bands in the A ~ 60 mass region are studied within cranked relativistic mean field theory and the configuration-dependent shell-correction approach based on the cranked Nilsson potential. Both approaches describe the experimental data well. Low values of the dynamic moments of inertia J^(2) compared with the kinematic moments of inertia J^(1) seen both in experiment and in calculations at high rotational frequencies indicate the high energy cost to build the states at high spin and reflect the limited angular momentum content in these configurations.

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Relativistic Mean Field Theory in Rotating Frame: Single-particle Properties at Superdeformation

Single-particle properties at superdeformation are investigated within the Cranked Relativistic Mean Field (CRMF) theory on the example of superdeformed rotational bands observed in the A~140-150 mass region. Applying the effective alignment approach it is shown that CRMF theory provides a reasonable description of the alignment properties of the single-particle orbitals. The agreement with experiment is good in most of the cases. This suggests that many features of the observed superdeformed bands can be well understood in terms of an almost undisturbed single-particle motion. The stability of the results with respect to the parameterizations used in Relativistic Mean Field (RMF) theory is also investigated, employing some frequently used non-linear effective forces. It turns out, with the exception of the single-particle ordering in superdeformed minimum, that the dependence of the calculated observables on the parameterization is rather small.

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Rotational Bands at the Limit of Angular Momentum

The properties of rotational bands at the limit of angular momentum are discussed on the example of smooth terminating bands observed in the A~110 mass region. The effective alignment approach is used for the study of their relative properties which provides additional insight into the properties of such bands.

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Cranked Relativistic Mean Field Description of Superdeformed Rotational Bands

The cranked relativistic mean field theory is applied for a detailed investigation of eight superdeformed rotational bands observed in $^{151}$Tb. It is shown that this theory is able to reproduce reasonably well not only the dynamic moments of inertia $J^{(2)}$ of the observed bands but also the alignment properties of the single-particle orbitals.

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Relative Properties of Smooth Terminating Bands

The relative properties of smooth terminating bands observed in the A~110 mass region are studied within the effective alignment approach. Theoretical values of $i_{eff}$ are calculated using the configuration-dependent shell-correction model with the cranked Nilsson potential. Reasonable agreement with experiment shows that previous interpretations of these bands are consistent with the present study. Contrary to the case of superdeformed bands, the effective alignments of these bands deviate significantly from the pure single-particle alignments < j_x > of the corresponding orbitals. This indicates that in the case of smooth terminating bands, the effects associated with changes in equilibrium deformations contribute significantly to the effective alignment.

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