A high-resolution measurement of the photofission spectrum of 232Th near threshold

Knowles, J.W.; Mills, W.F.; King, R.N.; Pich, B.O.; Yen, S.; Sobie, R. J.; Watt, L.A.K.; Drake, T.E.; Cardman, L. S.; Gulbranson, R. L.

doi:10.1016/0370-2693(82)90289-1

Cited by 40 publications

(36 citation statements)

References 9 publications

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“…for ultradeformed isomers) visible in some PESs (figs. [6][7][8][10][11][12] are not shown here. Where available, our predictions are compared with the experimental data [56,54].…”

Section: Electric Quadrupole Momentsmentioning

confidence: 99%

“…The analysis of the transmission probability of resonances in prompt fission induced by γ or light particles has suggested the existence of even more deformed isomeric states called hyper-deformed (hd). Such third minima were discovered in [230][231][232][233] Th [4][5][6][7][8][9], 232,234,236 U, and 232 Pa nuclei [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…. , 8) deformation parameters (in a spherical harmonics expansion). The Yukawa plus exponential model [18], and in parallel, the Lublin Strasbourg version of the liquid drop (LSD) [19], were used to evaluate the macroscopic part of the nuclear energy while the Woods-Saxon single-particle levels were used to obtain the microscopic energy correc- tions.…”

Section: Introductionmentioning

confidence: 99%

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On possible shape isomers in the Pt-Ra region of nuclei

Nerlo-Pomorska

Pomorski

Bartel³

et al. 2017

Eur. Phys. J. A

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Abstract.A certain number of yet unknown super-and hyper-deformed shape isomeric states are predicted in even-even nuclei of the region between Pt and Ra, using the macroscopic-microscopic model based on the Lublin Strasbourg Drop for the macroscopic energy and shell plus pairing corrections evaluated through the Yukawa-folded mean-field potential for the microscopic part. A new, rapidly converging shape parametrization is used to describe the vast range of nuclear deformations between the ground and the fission isomeric states up to near the scission configuration. Quadrupole moments are evaluated in the local minima and turn out to be in good agreement with the experimental data wherever available.

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“…for ultradeformed isomers) visible in some PESs (figs. [6][7][8][10][11][12] are not shown here. Where available, our predictions are compared with the experimental data [56,54].…”

Section: Electric Quadrupole Momentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On possible shape isomers in the Pt-Ra region of nuclei

Nerlo-Pomorska

Pomorski

Bartel³

et al. 2017

Eur. Phys. J. A

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“…These m inim a were used to explain the thorium anom aly [6][7][8]. H igh-resolution fission cross section m easurem ents for 230~233Th and 237U supported the existence o f shallow third m inim a on the P E S 's o f these nuclei [9][10][11][12][13][14][15]. T he deduced values for the depth o f the third w ell are only a few hundred keV.…”

Section: Introductionmentioning

confidence: 98%

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

et al. 2015

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Background: Potential energy surfaces (PES's) of actinide nuclei are characterized by a two-humped barrier structure. At large deformations beyond the second barrier, the occurrence of a third barrier was predicted by macroscopic-microscopic model calculations in the 1970s, but contradictory results were later reported by a number of studies that used different methods. Purpose: Triple-humped barriers in actinide nuclei are investigated in the framework of covariant density functional theory (CDFT). Methods: Calculations are performed using the multidimensionally constrained relativistic mean field (MDC-RMF) model, with the nonlinear point-coupling functional PC-PK1 and the density-dependent meson exchange functional DD-ME2 in the particle-hole channel. Pairing correlations are treated in the BCS approximation with a separable pairing force of finite range. Results: Two-dimensional PES's of 226.228.230,232 ancj 2 3 2 .2 3 4 .2 3 6 .2 3 8 y are mappe(i and the third minima on these surfaces are located. Then one-dimensional potential energy curves along the fission path are analyzed in detail and the energies of the second barrier, the third minimum, and the third barrier are determined. The functional DD-ME2 predicts the occurrence of a third barrier in all Th nuclei and 238U. The third minima in 230.2327}, are very shallow, whereas those in 226.2287}, and 238U are quite prominent. With the functional PC-PK1 a third barrier is found only in 226 .2 2 8 .2 3 0 7 }, single-nucleon levels around the Fermi surface are analyzed in 226Th, and it is found that the formation of the third minimum is mainly due to the Z = 90 proton energy gap at f 2o ~ 1 -5 and fto » 0.7. Conclusions: The possible occurrence of a third barrier on the PES's of actinide nuclei depends on the effective interaction used in multidimensional CDFT calculations. More pronounced minima are predicted by the DD-ME2 functional, as compared to the functional PC-PK1. The depth of the third well in Th isotopes decreases with increasing neutron number. The origin of the third minimum is due to the proton Z = 90 shell gap at relevant deformations.

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“…So far only very few photofission experiments in the past were conducted with γ beams of narrow energy bandwidth, such as a study of the photofission cross section in 232 Th using a tagged photon beam with an energy resolution of 14 keV [21]. Fission resonances were observed at excitation energies of 5.5 and 5.6 MeV, respectively.…”

Section: Exploring the Triple-humped Fission Barrier Via Photofissionmentioning

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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A high-resolution measurement of the photofission spectrum of 232Th near threshold

Cited by 40 publications

References 9 publications

On possible shape isomers in the Pt-Ra region of nuclei

On possible shape isomers in the Pt-Ra region of nuclei

Multidimensionally constrained relativistic mean-field study of triple-humped barriers in actinides

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

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