Barrier penetration and rotational damping of thermally excited superdeformed nuclei

Yoshida, Kōji; Shimizu, Yoshifumi R.

doi:10.1016/s0375-9474(01)01123-x

Cited by 30 publications

(33 citation statements)

References 61 publications

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“…The approach introduced here allows, by the particular choice of the two physically relevant orthogonal collective degrees of freedom associated with the mode along the fission path and the transverse vibrations, for a more realistic prediction of the shape of the one-dimensional effective fission barriers which can serve as an input to the calculations of fission half-lives within the traditional WKB method. As a consequence of the separation of the mentioned two modes, the reduction of the full two-dimensional vibrational Hamiltonian (9) to the one-dimensional one of the transverse variable x and the derivative ∂ ∂x is possible with the help of the transformation (14). In order to describe the vibrational excitations associated with the transverse collective movement, the reduced one-dimensional (GCM+GOA) collective Hamiltonian readŝ…”

Section: Collective Vibrations Across the Fission Pathmentioning

confidence: 99%

Microscopic Determinations of Fission Barriers (Mean-Field and Beyond)

Dobrowolski

Goutte

Berger

2007

Int. J. Mod. Phys. E

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With a help of the selfconsistent Hartree-Fock-Bogoliubov (HFB) approach with the D1S effective Gogny interaction and the Generator Coordinate Method (GCM) we incorporate the transverse collective vibrations to the one-dimensional model of the fission-barrier penetrability based on the traditional WKB method. The average fission barrier corresponding to the least-energy path in the two-dimensional potential energy landscape as function of quadrupole and octupole degrees of freedom is modified by the influence of the transverse collective vibrations along the nuclear path to fission. The set of transverse vibrational states built in the fission valley corresponding to a successively increasing nuclear elongation produces the new energy barrier which is compared with the least-energy barrier. These collective states are given as the eigensolutions of the GCM purely vibrational Hamiltonian. In addition, the influence of the collective inertia on the fission properties is displayed, and it turns out to be the decisive condition for the possible transitions between different fission valleys.

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Section: Collective Vibrations Across the Fission Pathmentioning

confidence: 99%

Microscopic Determinations of Fission Barriers (Mean-Field and Beyond)

Dobrowolski

Goutte

Berger

2007

Int. J. Mod. Phys. E

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“…for the average background contribution and 8) for the average fluctuation contribution to the average decay intensity. Eq.…”

Section: §1 Introductionmentioning

confidence: 99%

Energy Averages over Regular and Chaotic States in the Decay Out of Superdeformed Bands

Hussein

Sargeant

Pato

et al. 2004

Prog. Theor. Phys. Suppl.

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We describe the decay out of a superdeformed band using the methods of reaction theory. Assuming that decay-out occurs due to equal coupling (on average) to a sea of equivalent chaotic normally deformed (ND) states, we calculate the average intraband decay intensity and show that it can be written as an "optical" background term plus a fluctuation term, in total analogy with average nuclear cross sections. We also calculate the variance in closed form. We investigate how these objects are modified when the decay to the ND states occurs via an ND doorway and the ND states' statistical properties are changed from chaotic to regular. We show that the average decay intensity depends on two dimensionless variables in the first case while in the second case, four variables enter the picture. §1. IntroductionThe first superdeformed (SD) rotational band to be observed was that identified in the nucleus 152 66 Dy 86 by Twin et al. 1) A sequence of nineteen γ-rays of nearly constant spacing was observed which permitted the attribution of the moment of inertia of a symmetric prolate rigid rotor with elliptic axes in the proportion 1:1:2. Since then 320 SD bands have been observed in various mass regions extending from A∼20 to A∼240. 2) The stability of nuclei at any deformation can be related to the existence of energy gaps between shells of independent particle states. The shell gaps which appear for certain nuclear deformations give origin to non-spherical configurations of special stability. 3), 4)As explained by Lopez-Martens et al., 5) the γ-spectrum of a compound nucleus whose decay path includes an SD band typically contains γ-rays which result from four distinct stages: I Statistical γ-rays which populate the SD band after formation of the nucleus under consideration by particle evaporation following a fusion evaporation or fragmentation reaction. II Collective E2 γ-rays from decay along the SD band. III Statistical γ-rays from excited normally deformed (ND) configurations. IV Collective E2 γ-rays from decay along the yrast ND band. In cases where this kind of decay scheme applies, stages I and III correspond to the cooling of a hot and chaotic system while stages II and IV correspond to the decay of a cold and regular system. Other decay schemes which include SD bands are typeset using PTPT E X.cls Ver.0.89

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“…(17) of Ref. [20]. The level spacing d = 1/ρ FG , where ρ FG is the Fermi-gas density of states [also taken from Ref.…”

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confidence: 99%

“…The level spacing d = 1/ρ FG , where ρ FG is the Fermi-gas density of states [also taken from Ref. [20], Eq. (14)]; ρ FG was calculated at energies U above yrast with level density parameter a = 9.9 MeV −1 .…”

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Decay-out properties of a linked superdeformed band inZr84

et al. 2006

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Three discrete transitions were observed between the yrast superdeformed (SD) band and states of normal deformation (ND) in the nucleus 84 Zr. This is the first observation of such linking transitions in the mass-80 SD region. The properties of the decay out of the SD well in 84 Zr are compared with those in other SD mass regions. Calculations suggest that there is extensive mixing of configurations in the SD and ND potential minima, leading to an abrupt and highly fragmented decay-out process. A study of least-action tunneling paths indicates that the potential barrier separating the SD and ND wells is very small.

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Barrier penetration and rotational damping of thermally excited superdeformed nuclei

Cited by 30 publications

References 61 publications

Microscopic Determinations of Fission Barriers (Mean-Field and Beyond)

Microscopic Determinations of Fission Barriers (Mean-Field and Beyond)

Energy Averages over Regular and Chaotic States in the Decay Out of Superdeformed Bands

Decay-out properties of a linked superdeformed band inZr84

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