On the excitation energy of the ground state in the third minimum of U

Krasznahorkay, A.; Habs, D.; Hunyadi, M.; Gassmann, D.; Csatlós, M.; Eisermann, Y.; Faestermann, T.; Graw, G.; Gulyás, J.; Hertenberger, R.; Maier, H. J.; Máté, Z.; Metz, A.; Ott, Jörg; Thirolf, P.; Werf, S.Y. van der

doi:10.1016/s0370-2693(99)00826-6

Cited by 51 publications

(21 citation statements)

References 27 publications

(9 reference statements)

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“…Before reaching this third peak a third shallow minimum appears. Its shape is hyperdeformed and asymmetric, in agreement with the experimental data [4]. Later on, the proximity forces maintain the two fragments in contact and the shape of the smallest one evolves to prolate shapes (s < 1), the corresponding shell corrections decreasing.…”

Section: Ea(t) Ea(e) E2(t) E2(e) E B (T) E B (E) E3(th) Ec(t) Plateausupporting

confidence: 86%

“…This fact is a severe test for the theoretical models. Furthermore, the analysis of the fission probability and of the angular distribution of the fragments indicate the existence of hyperdeformed states in a deep third well in several Th and U isotopes [3][4][5] confirming the pioneering work of Blons et al [6] in 231,233 Th. The observed strongly enhanced low energy α decay of several heavy actinide nuclei is also understood assuming the decay of a third hyperdeformed minimum and the possibility that the third minimum is the true ground state of very heavy and perhaps superheavy nuclei has been also advocated [7].…”

Section: Introductionsupporting

confidence: 63%

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Fission barriers and half-lives of actinides in the quasimolecular shape valley

2012

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The energy of actinide nuclei in the fusionlike deformation valley has been determined from a liquid drop model taking into account the proximity energy, the mass and charge asymmetries and the shell and pairing energies. Double-humped potential barriers appear. The saddle-point corresponds to the second maximum and to the transition from compact one-body shapes with a deep neck to two touching ellipsoids. The scission point, where the effects of the nuclear attractive forces between the fragments vanish, lies at the end of an energy plateau below the saddle-point and corresponds to two well separated fragments. The kinetic and excitation energies of the fragments come from the energy on this plateau. The shell and pairing effects play a main role to decide the most probable decay path. The heights of the potential barriers roughly agree with the experimental data and the calculated half-lives follow the trend of the experimental values. A shallow third minimum and a third peak appear in specific asymmetric exit channels where one fragment is close to a double magic quasi-spherical nucleus, while the other one evolves from oblate to prolate shapes.

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Section: Ea(t) Ea(e) E2(t) E2(e) E B (T) E B (E) E3(th) Ec(t) Plateausupporting

confidence: 86%

Section: Introductionsupporting

confidence: 63%

Fission barriers and half-lives of actinides in the quasimolecular shape valley

2012

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“…axis ratio 3:1) third potential minimum remained unclear. In a series of measurements, employing light-particle induced direct reactions, in the isotopic chain of even-even uranium nuclei [13][14][15] (and recently in 232 Pa for the first time also in an odd-A isotope [16]), we succeeded to establish the existence of a deep third potential minimum, in some cases comparably deep as the second minimum. Since for hyperdeformed configurations the rather thin outer barrier results in fission lifetimes much shorter than typical lifetimes of collectively excited states in the excita- Energy (MeV) 00 00 00 11 11 11 00 00 00 11 11 11 000 000 000 111 111 111 00 00 00 00 11 11 11 11 00 00 00 00 11 11 11 11 000 000 000 000 111 111 111 111 00 00 00 00 11 11 11 11 00 00 00 00 11 11 11 11 000 000 000 000 111 111 111 111 000 000 000 111 111 111 000 000 000 111 111 111 000 000 000 111 111 111 00 00 00 11 11 11 00 00 00 11 11 11 000 000 000 000 111 111 111 111 00 00 00 00 11 11 11 11 000 000 000 000 111 111 111 111 000 000 000 111 111 111 00 00 00 00 11 11 11 11 00 00 00 11 11 11 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 000 000 000 111 111 111 000 000 000 000 111 111 111 111 00 00 00 11 11 11 00 00 00 11 11 11 00 00 00 00 11 11 11 11 000 000 000 000 111 111 111 111 00 00 00 11 11 11 00000 00000 11111 11111 00000 00000 00000 11111 11111 11111 00000 00000 11111 11111 Fig.…”

Section: The Multiple-humped Potential Barrier In the Actinidesmentioning

confidence: 99%

“…Multiple-humped potential energy curves of even-even isotopes of thorium, uranium and plutonium, as obtained from theoretical calculations by Howard and Möller (for the first and second minima) [17] and by Cwiok et al [18] for the hyperdeformed third minimum. Black dots denote experimental data for barrier height and potential minima, respectively [13][14][15]19].…”

Section: The Multiple-humped Potential Barrier In the Actinidesmentioning

confidence: 99%

Perspectives for photofission studies with highly brilliant, monochromaticγ–ray beams

Thirolf

Csige

Habs

et al. 2012

EPJ Web of Conferences

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Abstract. New research facilities like MEGa-Ray (Livermore) or ELI-NP (Bucharest) will provide within the next years (2013)(2014)(2015)(2016) photon beams of unprecedented quality with respect to both photon intensity (total flux ∼ 10 13 γ/s) and spectral intensity (∼ (10 4 -10 6 )/eVs), thus exceeding the performance of existing facilities by several orders of magnitude. This tremendous progress will be enabled by Compton-backscattering of an intense laser off a high-quality electron beam, in conjunction with novel refractive bremsstrahlung beams focusing γ optics and efficient monochromatization techniques. We envisage to employ these γ beams for photofission studies on extremely deformed nuclear states of actinides, investigating their multiple-humped potential energy landscape in a highly selective way. Transmission resonances in the prompt fission cross section from the (superdeformed) second and (hyperdeformed) third potential minimum will be studied, where the fission decay channel can be expressed as a tunnelling process of these gateway states through the multiple-humped fission barrier. Novel brilliant γ beams for photonuclear sciencePhotonuclear physics is a well-established field of research since decades [1]. Mostly bremsstrahlung has been used to excite nuclei or to induce fission in the actinides [2]. A significant improvement in narrowing the energy resolution of photon beams from typically 200-300 keV at bremsstrahlung facilities to about 15-25 keV was achieved by introducing the tagged-photon technique [3]. In recent years increasingly also Compton-backscattering of (laser-) photons off an energetic electron beam was used to generate γ beams according to the scheme illustrated by figure 1. Here the Doppler-upshift experienced by the initial pho- Fig. 1. Sketch of the mechanism to produce MeV photon beams (E γ ) by exploiting the Doppler-upshift experienced by a laser photon (energy E 0 ) which is Compton-backscattered off a relativistic electron. ton with energy E 0 is exploited to generate photon beams with high energies E γ via Compton-backscattering from a counter-propagating fast electron beam, characterized by its relativistic factor γ according to a e-mail: Peter.Thirolf@lmu.deThe simplified scaling of the backscattered photon energy with 4γ 2 holds for exactly backscattered photons and takes into account that the recoil term 4γE 0 /mc 2 is negligible for initial photon energies of a few eV. In realistic experiments, the angular spread after Compton scattering, described within the Klein-Nishina formula by the angle θ between the incident laser direction and the direction of the scattered γ beam, will be reduced by appropriate collimation of the back-scattered photons.Presently the world-leading γ-beam facility HIγS (High Intensity Gamma-Ray Source) is operated at Duke University in the US [4]. A free-electron laser (FEL) operated in a 1.2-GeV electron storage ring is used to produce photons (from IR to VUV) that subsequently are Comptonbackscattered off the relativistic electron beam. Cu...

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“…The fission probability and the angular distribution of the fragments suggest also the existence of hyperdeformed states in a deep third well in several Th and U isotopes [1,2]. It is also necessary to suppose fission barrier heights of 5-10 MeV to explain the stability of superheavy elements of charge 112-118 [3,4].…”

Section: Introductionmentioning

confidence: 99%

Fission of actinides through quasimolecular shapes

Royer¹,

Zhang

Eudes³

et al. 2013

EPJ Web of Conferences

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Abstract. The potential energy of heavy nuclei has been calculated in the quasimolecular shape path from a generalized liquid drop model including the proximity energy, the charge and mass asymmetries and the microscopic corrections. The potential barriers are multiplehumped. The second maximum is the saddle-point. It corresponds to the transition from compact one-body shapes with a deep neck to two touching ellipsoids. The scission point lies at the end of an energy plateau well below the saddle-point and where the effects of the nuclear attractive forces between two separated fragments vanish. The energy on this plateau is the sum of the kinetic and excitation energies of the fragments. The shell and pairing corrections play an essential role to select the most probable fission path. The potential barrier heights agree with the experimental data and the theoretical half-lives follow the trend of the experimental values. A third peak and a shallow third minimum appear in asymmetric decay paths when one fragment is close to a double magic quasispherical nucleus, while the smaller one changes from oblate to prolate shapes.

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On the excitation energy of the ground state in the third minimum of U

Cited by 51 publications

References 27 publications

Fission barriers and half-lives of actinides in the quasimolecular shape valley

Fission barriers and half-lives of actinides in the quasimolecular shape valley

Perspectives for photofission studies with highly brilliant, monochromaticγ–ray beams

Fission of actinides through quasimolecular shapes

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