Bimodal symmetric fission observed in the heaviest elements

Abstract. Static self-consistent methods usually allow to determine the most probable fission fragments mass asymmetry. We have applied random neck rupture mechanism to the nuclei in the configuration at the end of fission paths. Fission fragment mass distributions have been deduced from the prescission nuclear density distribution obtained from the self-consistent calculations. Potential energy surfaces as well as nuclear shapes have been calculated in the fully microscopic theory, namely the constrained Hartree-Fock-Bogolubov model with the effective Gogny D1S density-dependent interaction. The method has been applied for analysis of fission of 256,258 Fission fragment mass yield deduced from density distribution in the pre-scission configuration 2

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“…It was shown, that fission in 258 Fm represents specific, bimodal character [30,31]. Its mass yield is very narrow with a single peak.…”

Section: Resultsmentioning

confidence: 99%

Fission fragment mass yield deduced from density distribution in the pre-scission configuration

Warda

Zdeb

2015

Phys. Scr.

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“…4 We found the total kinetic energy (TKE) distributions of the fragments strongly deviated from the Gaussian distributions which are observed in the fission of lighter actinides. In four of five nuclides studied, the anomalous TKE distribution was skewed sufficiently that it could be decomposed into two Gaussian distri butions.…”

Section: Introductionmentioning

confidence: 74%

“…We have suggested that the liquid-drop and the "fragment shell" process es are separately responsible for the distinct portions of the TKE distributions. 4 The high-TKE mode depends on the Influence of frag ment shells which are emerging between the saddle and scission point. *' 3 Fragment shells near the doubly-magic 13Z Sn lower the potential-energy path and, thus, guide the mass division toward Sn isotopes near the 82-neutron closed shell.…”

Section: Methodsmentioning

confidence: 99%

Evidence for bimodal fission in the heaviest elements

Hulet¹

1987

AIP Conference Proceedings

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We have measured the mass and kinetic-energy partitioning in the spontaneous fission of five heavy nuclides: 258 [104], were measured on-line by a special rotating-wheel instru ment, while the others were determined off-line after mass separa tion.All fissioned with mass distributions that were symmetric. Total-kinetic-energy distributions peaked near either 200 or 235 MeV. Surprisingly, because only a single Gaussian energy distribution had been observed previously in actinide fission, these energy distri butions were skewed upward or downward from the peak in each case, except for 260 [104], indicating a composite of two energy distribut ions. We were able to fit accurately two Gaussian curves to the gross energy distributions from the four remaining nuclides. From the multiple TKE distributions and the shapes of the mass distribu tions, we conclude that there is a low-energy fission component with liquid-drop characteristics which is admixed with a much higherenergy component due to closed fragment shells. We now have further evidence for this conclusion from measurements of the neutron multi plicity in the spontaneous fission of 26 "Md.

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“…Multimodal nature of fission in low-energy and spontaneous fission of heavy nuclei has been widely recognized today as a concept describing the properties of mass-energy distributions (MEDs) of the fission fragments [1,2,3,4]. A few years ago our effort has been concentrated on the investigation of the multimodal structure of the fission fragments MED for the nuclear 216,220 Ra [5,6], and 220,224,226 Th [7,8,9].…”

Section: Introductionmentioning

confidence: 99%

The fusion-fission process in the reaction 34S+186W near the interaction barrier

Harca

Dmitriev

Itkis

et al. 2015

AIP Conference Proceedings

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Abstract. The reaction 34 S + 186 W at E lab =160 MeV was investigated with the aim of diving into the features of the fusion-fission process. Gamma rays in coincidence with binary reaction fragments were measured using the high efficiency gamma-ray spectrometer ORGAM at the TANDEM Accelerator facility of I.P.N., Orsay, and the time-of-flight spectrometer for fission fragments (FF) registration CORSET of the Flerov Laboratory of Nuclear Reactions (FLNR), Dubna. The coupling of the ORGAM and CORSET setups offers the unique opportunity of extracting details for characterizing the fusion-fission process and gives information regarding production of neutron-rich heavy nuclei. The FF−γ coincidence method is of better use then the γ − γ coincidence method when dealing with low statistic measurements and also offers the opportunity to precisely correct the Dopler shift for in-flight emitted gamma rays. Evidence of symmetric and asymmetric fission modes were observed in the mass and TKE distributions, occurring due to shell effects in the fragments. Coincident measurements allow for discrimination between the gamma rays by accepting a specific range within the mass distribution of the reaction products. Details regarding the experimental setup, methods of processing the acquisitioned data and preliminary results are presented.

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Bimodal symmetric fission observed in the heaviest elements

Cited by 227 publications

References 19 publications

Fission fragment mass yield deduced from density distribution in the pre-scission configuration

Fission fragment mass yield deduced from density distribution in the pre-scission configuration

Evidence for bimodal fission in the heaviest elements

The fusion-fission process in the reaction 34S+186W near the interaction barrier

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