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Zhang, H. X.; Yeh, T.R.; Lancman, H.

doi:10.1103/physrevc.34.1397

Cited by 23 publications

(26 citation statements)

References 24 publications

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“…[44]. The experimental values are from [45], [39], [2], and [42]. The values in parentheses are the zero-point energies substracted in those references.…”

Section: Discussionmentioning

confidence: 99%

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Fission barriers and asymmetric ground states in the relativistic mean-field theory

Rutz

Maruhn²,

Reinhard³

et al. 1995

Nuclear Physics A

127

124

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The symmetric and asymmetric fission path for 240 Pu, 232 Th, and 226 Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativstic calculations. Furthermore, stable octupole deformations in the ground states of Radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativsitic parametrizations. I. INTRODUCTIONNuclear fission has been the challenge to develop microscopic theories of nuclear collective motion. Only a subtle interplay of collective deformations and changing microscopic 1 shell structure can explain the quantitative details like tunneling times and fragment mass distributions [1]. One of the most decisive features to pin down the contributions from the shell effects is the occurence of multiple-humped barriers [2]. The macroscopic-microscopic method, based on a phenomenologically fitted shell model plus Strutinsky shell corrections [3], allowed quite early extensive investigations of the various landscapes of collective Potential Energy Surfaces (PES), see e. g. [1,[4][5][6][7]. Since the early seventies, fully selfconsistent mean-field models have been available for nuclei. These are the nonrelativistic Hartree-Fock models with the Skyrme force [8,9] or the Gogny force [10]. At about the same time competitive relativistic mean-field models for nuclear structure were proposed [11,12]. Although much more elaborate, selfconsistent mean-field calculations of the PES for nuclear fission appeared rather soon for the Skyrme-Hartree-Fock models [13] and later for the Gogny force [14], it was only recently that PES for fission have been calculated with the relativistic mean-field model [15]. These calculations have shown that well adjusted parametrizations for the relativistic mean-field model, see e. g. [16,17], deliver reasonable fission barriers comparable to those of nonrelativistic calculations. A variation of the parametrization, in particular with respect to the effective mass, has shown that the requirement to reproduce reasonable fission barriers excludes many variants and only the standard best-fit forces with the typically very low effective nucleon mass remain. It is the aim of this paper to extend the investigations of [15] to asymmetric fission and to study a larger variety of actinides.We confine the consderations to the two parametrizations NL1 from [16] and PL-40 from [18] which have proven to provide reasonable fission barriers [15]. In addition, we consider the parametrization NL-SH which is claimed to be better adjusted with respect to isovector properties [19]. As a second objective of this paper, we exploit the asymmetric degree of freedom in our calculations to investigate the possibility of stable octupole deformations in the ground s...

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“…[44]. The experimental values are from [45], [39], [2], and [42]. The values in parentheses are the zero-point energies substracted in those references.…”

Section: Discussionmentioning

confidence: 99%

“…The third barrier seems to be experimentally supported [41]. It is indicated e. g. by the photofission cross-section [42], or by the asymmetric angular distribution of the light fragment [43]. Fig.…”

Section: Fission Of Heavy Elementsmentioning

confidence: 99%

Fission barriers and asymmetric ground states in the relativistic mean-field theory

Rutz

Maruhn²,

Reinhard³

et al. 1995

Nuclear Physics A

127

124

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“…34 Since a highly relativistic current of electrons is produced in a dense plasma having ions of a high charge Z by the interaction of the oscillating electrons with the solid target, it is expected that a substantial quantity of energetic bremsstrahlung will be generated, some of which will be in the energy range (-10 MeV) corresponding to the photofission 20,21 process (1). Furthermore, since oy-\0 2 o e u the contribution of the photofission channel may not necessarily be negligible.…”

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confidence: 99%

Possibility of optically induced nuclear fission

1988

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The process of nuclear fission induced by nonlinear radiative coupling to atomic electrons is considered. For 248-nm radiation at an intensity of -10 21 W/cm 2 , highly relativistic currents are produced which can couple to the fission mode of nuclear decay. With irradiation for a time of -100 fs, the results indicate a fission probability of -10 ~5 for 2 $U nuclei located at the surface of a solid target, a value several orders of magnitude above the limit of detection. PACS numbers: 25.85.Ge, 32.80.Wr Nuclear fission can be induced by electromagnetic interactions involving either photons or charged particles if sufficient energy is communicated to the nucleus enabling the system to penetrate the fission barrier. Known examples of electromagnetically induced fission are photofission, 1,2 rr-^/,+/ 2 +V72, (1) electrofission, 3 e~+A-+ fi+f 2 + fn + e~,and muon-induced fission. 4 ' 5 It has also recently been proposed 6,7 that driven motions of atomic electrons arising from intense irradiation of atoms can couple energy to nuclear transitions occurring between bound nuclear states. This latter mechanism has some features in common with processes of nuclear excitation and deexcitation in which atomic electronic transitions play a role. 8 " 13 The present work examines the possibility of optically induced nuclear fission of heavy elements arising from coupling to driven motions of atomic electrons produced by intense external radiation. The fission process is a particularly favorable one for the demonstration of nuclear excitation. It (1) generally has a large nuclear matrix element, (2) is a broad channel permitting coupling to spectral power over a wide range, and (3) involves a very large energy release comprising distinctive emissions. It will be shown that very large instantaneous fission rates may be generated in a considerable range of nuclear materials. If this can be achieved, extremely bright and spatially localized high-flux pulsed sources of fission fragments, neutrons, and y radiation could be produced (e.g., > 10 24 fission fragments/cm 2 s).The acceleration of electrons to an energy sufficient to surpass the threshold of the fission reaction can be achieved in the focal region of an intense laser pulse. 14,15 The availability of an ultraviolet laser technology 16,17 capable of producing subpicosecond pulses with energies approaching the joule level in low-divergence beams at high repetition rates is making possible a regime of physical study concerning the behavior of matter at extremely high intensities 18,19 in the 10 20 -10 21 -W/cm 2 range. Since it can be shown 14,15 that intensities comparable to 5x 10 19 W/cm 2 at 248 nm will cause strongly relativistic motions to occur, the use of an intensity of =10 21 W/cm 2 would then generate relativistic electrons 14,15 with an energy sufficient (/-24) to produce electrofission by the collisional mechanism represented by reaction (2). We also note that the bremsstrahlung produced collaterally by the fast electrons in the target material can also participat...

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“…The 232 Th(γ,f) reaction cross section results are listed in Table II and plotted in Fig.14, along with all available literature data sets which extend below an excitation energy of 6 MeV [15,16,40,[43][44][45][46] and the ENDF/B-VIII.0 evaluation [47]. Data sets consistent with 0 mb below ∼ 6 MeV [48][49][50][51][52] were omitted.…”

Section: Photofission Cross Sectionsmentioning

confidence: 99%

“…However a deep third minimum of ∼ 2 MeV in the 232 Th fission barrier was obtained by Blokhin and Soldatov [14] by analyzing photofission cross sections extracted from data obtained by unfolding bremsstrahlung beams [15]. In light of the experimental evidence of deep third minima in the fission barriers of U isotopes, older 232 Th photofission data [16] was reinterpreted by Thirolf et al [17] to tentatively show a ∼ 4 MeV deep third minimum, roughly equal in depth to the second minimum. The prospects for further re-analysis of older 232 Th photofission cross section data are limited by the large discrepancies between data sets, particularly in the sub-barrier energy region where the effects of the fission barrier structure are most pronounced [18].…”

Section: Introductionmentioning

confidence: 99%

Near-barrier photofission in Th232 and U238

Silano

Karwowski

2018

Phys. Rev. C

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A study of photofission of 232 Th and 238 U was performed using quasi-monoenergetic, linearlypolarized γ-ray beams from the High Intensity γ-ray Source at Triangle Universities Nuclear Laboratory. The prompt photofission neutron polarization asymmetries, neutron multiplicities and the photofission cross sections were measured in the near-barrier energy range of 4.3-6.0 MeV. This data set constitutes the lowest energy measurements of those observables to date using quasimonoenergetic photons. Large polarization asymmetries are observed in both nuclei, consistent with the E1 excitation as observed by another measurement of this kind made in a higher energy range. Previous experimental evidence of a deep third minimum in the 238 U fission barrier has been identified as an accelerator-induced background.

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Photofission cross section ofTh232

Cited by 23 publications

References 24 publications

Fission barriers and asymmetric ground states in the relativistic mean-field theory

Fission barriers and asymmetric ground states in the relativistic mean-field theory

Possibility of optically induced nuclear fission

Near-barrier photofission in Th232 and U238

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