Nuclear dissipation effects on fission and evaporation in systems of intermediate fissility

Nadotchy, P.N.; Brondi, A.; Nitto, A. Di; Rana, G. La; Moro, R.; Vardaci, E.; Ordine, A.; Boiano, A.; Cinausero, M.; Prete, G.; Rizzi, V.; Gelli, N.; Lucarelli, F.

doi:10.1051/epjconf/20100208003

Cited by 10 publications

(13 citation statements)

References 12 publications

(20 reference statements)

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“…and energy spectra obtained in Ref. [29] for fission fragments from 200-MeV 32 S on 100 Mo. The measured average energy is 68.7 MeV, to which should be added about 3 MeV from stopping in the target, and the result is 2 MeV above the value calculated from a total fission energy release of 46 MeV per fragment [29].…”

Section: A Energy Spectramentioning

confidence: 76%

“…This may be justified by the fact that the maximum value of the spin is otherwise much larger than the critical value, I c , corresponding to B f = 0. This is not the case for 32 S bombardment and the discrepancy between measured and calculated cross sections must for this case be found elsewhere, perhaps in the competition from emission of light, charged particles [29][30][31]. The omission of these channels in the simulations is a deficiency but it appears difficult to include them in a consistent manner [30,31].…”

Section: Statistical Simulations Of Fissionmentioning

confidence: 97%

“…[29][30][31]. The sensitivity of the long-lifetime component to η is smaller for 48 Ti and 58 Ni bombardment because there is a high-spin region with very low fission barrier and predominantly first-chance fission.…”

Section: Statistical Simulations Of Fissionmentioning

confidence: 99%

“…The fill-in of the blocking-dip minimum is due to fission after emission of several neutrons (here two to four). For simplicity, we ignore emission of light, charged particles 044609-6 (protons and α particles), although it is known that this can be a significant channel for the fused nuclei [29][30][31]. Our aim is mainly to investigate whether the blocking results are consistent with the standard picture of multichance fission and a very broad lifetime distribution.…”

Section: Statistical Simulations Of Fissionmentioning

confidence: 99%

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Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

et al. 2012

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Time delays in fission induced by bombardment of Mo with 170-and 180-MeV 32 S, 225-and 240-MeV 48 Ti, and 300-MeV 58 Ni have been measured by observation of crystal blocking of fission fragments. In contrast to earlier measurements with a W target, the results are consistent with fission of a compound nucleus in competition with mainly neutron emission. Most of the fissions happen on a time scale much shorter than attoseconds but there is a significant component of fission with much longer lifetimes. The measurements are reproduced with a standard statistical model, including a Kramers correction to fission widths from the viscosity of hot nuclear matter. These new results support the interpretation of our earlier measurements with a W target, which indicate that there is a transition in heavy-ion-induced fission at large atomic number and mass, from multichance fission in the standard Bohr-Wheeler picture to fission without formation of a compound nucleus. The process is slowed down by nuclear viscosity, with measured delays of order attoseconds.

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Section: A Energy Spectramentioning

confidence: 76%

Section: Statistical Simulations Of Fissionmentioning

confidence: 97%

Section: Statistical Simulations Of Fissionmentioning

confidence: 99%

Section: Statistical Simulations Of Fissionmentioning

confidence: 99%

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Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

et al. 2012

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“…This improvement would be of interest also in case of modeling dynamically the descent from saddle to scission by means of Langevin framework. Indeed, various observables relevant to the fission dynamics have been thoroughly studied in the case of binary decay of 132 Ce [27], a compound nucleus close to the 118 Ba nucleus. While a wide set of observables could be reproduced by the model assuming the time evolution of the system on potential energy surface given by the three dimensions FRLDM, the model fails to explain the TKE distribution with underestimation of the variance by about 40%.…”

Section: Discussionmentioning

confidence: 99%

Asymmetric Fission in the⁷⁸Kr+⁴⁰Ca reactions at 5.5 MeV/nucleon

Bec

Wieleczko

Adémard

et al. 2012

EPJ Web of Conferences

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Abstract.The cross section, kinetic energy distribution and angular distribution of fragments with atomic number 3 ≤ Z ≤ 28 emitted in the reaction 78 Kr + 40 Ca at the bombarding energy of 5.5 MeV/nucleon and coincidence between light charged particles and fragments were measured by means of the 4π-INDRA array to study the decay mechanism of medium mass excited nucleus. Global features indicate a high degree of relaxation and are compatible with a binary fission from compound nucleus. The mean value of the kinetic energy distributions of fragments indicates dominance of Coulomb interaction, while the width of the distribution signals large fluctuations. Inclusive cross-section distributions of fragments with charge 3 ≤ Z ≤ 28 are bell-shaped and a strong even-odd-staggering (o-es) is observed for 3 ≤ Z ≤ 12. Coincidence measurements suggest that the light partners in very asymmetric fission are emitted at excitation energies below the particle emission thresholds. Data were confronted to the predictions of statistical model describing the decay of compound nuclei by emission of light particles and fragments. Calculations assuming spherical fission fragments and finite-range liquid drop fission barriers are not able to explain the experimental features. Attempts have been made to improve the agreement with experimental data. The analysis indicates the strong influence of the shape parameterization of the potential energy surface in describing the fission process of intermediate mass compound nuclei. a

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Evaporation channel as a tool to study fission dynamics

et al. 2018

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The dynamics of the fission process is expected to affect the evaporation residue cross section because of the fission hindrance due to the nuclear viscosity. Systems of intermediate fissility constitute a suitable environment for testing such hypothesis, since they are characterized by evaporation residue cross sections comparable or larger than the fission ones. Observables related to emitted charged particle, due to their relatively high emission probability, can be used to put stringent constraints on models describing the excited nucleus decay and to recognize the effects of fission dynamics. In this work model simulations are compared with the experimental data collected via the 32 S + 100 Mo reaction at E lab = 200 MeV. By comparing an extended set of evaporation channel observables the limits of the statistical model and the large improvement coming by using a dynamical model are evidenced. The importance of using a large angular covering apparatus to extract the observable is stressed. The opportunity to measure more sensitive observables by a new detection device in operation at LNL are also discussed.

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Nuclear dissipation effects on fission and evaporation in systems of intermediate fissility

Cited by 10 publications

References 12 publications

Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

Asymmetric Fission in the⁷⁸Kr+⁴⁰Ca reactions at 5.5 MeV/nucleon

Evaporation channel as a tool to study fission dynamics

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Nuclear dissipation effects on fission and evaporation in systems of intermediate fissility

Cited by 10 publications

References 12 publications

Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

Time delays in heavy-ion-induced fission of medium-Znuclei, measured by crystal blocking

Asymmetric Fission in the78Kr+40Ca reactions at 5.5 MeV/nucleon

Evaporation channel as a tool to study fission dynamics

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Product

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Asymmetric Fission in the⁷⁸Kr+⁴⁰Ca reactions at 5.5 MeV/nucleon