New Spontaneous Fission Mode for<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>252</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi>Cf</mml:mi></mml:math>: Indication of Hyperdeformed<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>1</mml:mn><mml:mn>4</mml:mn><mml:mn>4</mml:mn><mml:mo>,</mml:mo><mml:mn>1</mml:mn><mml:mn>4</mml:mn><mml:mn>5</mml:mn><mml:mo>,

Ter-Akopian, G. M.; Hamilton, J. H.; Oganessian, Yu. Ts.; Daniel, A. V.; Kormicki, J.; Ramayya, A. V.; Popeko, G. S.; Babu, B. R. S.; Lu, Qi; Butler-Moore, K.; Ma, W.C.; Ćwiok, S.; Nazarewicz, W.; Deng, J. K.; Shi, D.; Kliman, J.; Morháč, M.; Cole, J. D.; Aryaeinejad, R.; Johnson, Noah R.; Lee, I. Y.; McGowan, F.K.; Saladin, J. X.

doi:10.1103/physrevlett.77.32

Cited by 61 publications

(31 citation statements)

References 12 publications

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“…Many of them are allowed, however, in the superdeformed and hyperdeformed states. This finding also indicates that the spontaneous fission takes place via the (tiny) component of the ground-state wave function which corresponds to an extremely deformed state, similarly to the conjecture of [26]. (Please, note that the effective quantum numbers correspond to a kind of average, which may contain contribution from many pure SU(3) states, i.e.…”

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confidence: 85%

Ternary clusterization and quadrupole deformation

et al. 2006

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The deformation-dependence of ternary clusterization of atomic nuclei is investigated. In particular, allowed and forbidden ternary clusterconfigurations are determined for the ground, superdeformed, and hyperdeformed states of some light and heavy nuclei, based on a microscopic (real and effective SU(3)) selection rule. The energetic stability of the clusterizations is also considered. The investigation of exotic nuclear shapes, e.g. superdeformed and hyperdeformed states is one of the most interesting topics in recent nuclear structure studies. The appearance of exotic cluster configurations (or exotic cluster decay) is another issue of utmost interest. The combination of these two problems brings us to an exciting question: what is the interrelation of these two phenomena, i.e. what are the possible clusterizations of nuclear states with exotic shapes. In the present Letter we address this question from the angle of the ternary clusterization. We apply methods which can be generalized to more complicated multicluster-configurations in a straightforward way.The basic concept of this work is that when we try to describe the composition of an atomic nucleus from smaller nuclei (clusters) then we take into account both of the two complementary natural laws, which govern this kind of phenomenon: the energy-minimum principle and the Pauli-exclusion principle. The crucial role of these two rules are obvious: energetically unfavored systems are not likely to appear, and when the building blocks are fermions, like the nucleons of the atomic nuclei, then they follow the exclusion principle. However, the exact role, or * Corresponding author.E-mail address: algora@atomki.hu (A. Algora).relative importance of these two aspects of clusterization among different circumstances are not completely understood yet; the present work is meant to be a contribution to this task. Much attention has been paid to the energetic preference of various cluster-configurations of a nucleus. The methods applied along this line are partly or completely empirical ones, using information gained from the experimental data. Furthermore, most of these works concentrate on the simplest, i.e. binary clusterizations, especially, when the energetic calculation involves (in addition to the experimental binding energies) intercluster potentials, like in the dinuclear system model [1], or in the local potential approach [2]. On the other hand the treatment of the exclusion-principle has to be done microscopically, therefore, apart from the light, or simplest heavy nuclei, it gives rise to large computational difficulties. Due to this fact no systematic studies has been done, and many of the experimentally interesting systems are untouched from this viewpoint.The main point of this Letter is to present a method for the approximative treatment of the exclusion principle, which can be applied both to binary [3] and to ternary (and even to multi) cluster-configurations. The results of these calculations can be combined with those on the energetic sta...

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Ternary clusterization and quadrupole deformation

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“…Pronounced third minima have been predicted in theoretical studies of the thorium and uranium isotopes, especially those carried out with the macroscopic-microscopic (MM) approach [6,7,26,27,29,30]. On the other hand, self-consistent studies based on the nuclear density functional theory [31][32][33][34][35], as well as recent MM work [36], typically find a third minimum that is much shallower than that of the earlier MM calculations or the empirical barrier fits [37,38].…”

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Third minima in thorium and uranium isotopes in a self-consistent theory

2013

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Background: Well-developed third minima, corresponding to strongly elongated and reflection-asymmetric shapes associated with dimolecular configurations, have been predicted in some non-self-consistent models to impact fission pathways of thorium and uranium isotopes. These predictions have guided the interpretation of resonances seen experimentally. On the other hand, self-consistent calculations consistently predict very shallow potential energy surfaces in the third minimum region.Purpose: We investigate the interpretation of third-minimum configurations in terms of dimolecular (cluster) states. We study the isentropic potential energy surfaces of selected even-even thorium and uranium isotopes at several excitation energies. In order to understand the driving effects behind the presence of third minima, we study the interplay between pairing and shell effects. Methods:We use the finite-temperature superfluid nuclear density functional theory. We consider two Skyrme energy density functionals: a traditional functional SkM * and a recent functional UNEDF1 optimized for fission studies.Results: We predict very shallow or no third minima in the potential energy surfaces of 232 Th and 232 U. In the lighter Th and U isotopes with N = 136 and 138, the third minima are better developed. We show that the reflection-asymmetric configurations around the third minimum can be associated with dimolecular states involving the spherical doubly-magic 132 Sn and a lighter deformed Zr or Mo fragment. The potential energy surfaces for 228,232 Th and 232 U at several excitation energies are presented. We also study isotopic chains to demonstrate the evolution of the depth of the third minimum with neutron number. Conclusions:We show that the neutron shell effect that governs the existence of the dimolecular states around the third minimum is consistent with the spherical-to-deformed shape transition in the Zr and Mo isotopes around N = 58. We demonstrate that the depth of the third minimum is sensitive to the excitation energy of the nucleus. In particular, the thermal reduction of pairing, and related enhancement of shell effects, at small excitation energies help to develop deeper third minima. At large excitation energies, shell effects are washed out and third minima disappear altogether.

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“…In some recent gamma-ray spectroscopy studies in 252 Cf spontaneous fission, enhanced cross-sections have been reported [2,3] for the production of Ba-Mo fragment pairs associated with high neutron emission multiplicities (ν n ) of 7 to 10 neutrons. To explain this observation, it was inferred that the 144,145,146 Ba fragments at scission exhibit an unusually large deformation characterized by a 3:1 axis ratio, while their Mo partners have a normal, only slightly deformed shape.…”

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Study of the Mo-Ba partition in 252Cf spontaneous fission

Biswas

Choudhury

Cinausero

et al. 2000

EPJ A

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Measurements of fission fragment yields and neutron multiplicities have been carried out for the Mo-Ba fragment pairs in the spontaneous fission of 252 Cf, using the γ-ray spectroscopy technique to analyze γ-γ-γ coincidence data. Prompt γ-ray multiplicities were also measured as a function of the number of neutrons emitted in the fission process leading to the Mo-Ba partition. We do not observe the enhancement in the yields of events with high neutron emission multiplicity (νn≥7) that has been associated to a second fission mode leading to the production of hyperdeformed Ba fragments, as reported in some earlier studies. The average γ-ray multiplicity is found to be rather weakly dependent on the number of neutrons emitted in the fission process. PACS. 27.70.+q 150 ≤ A ≤ 189 -21.10.Re Collective levels -25.70.Gh Compound nucleus

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New Spontaneous Fission Mode for252Cf: Indication of Hyperdeformed144,145,

Cited by 61 publications

References 12 publications

Ternary clusterization and quadrupole deformation

Ternary clusterization and quadrupole deformation

Third minima in thorium and uranium isotopes in a self-consistent theory

Study of the Mo-Ba partition in 252Cf spontaneous fission

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