Fission probability calculations for heavy-ion induced reactions

Delagrange, H.; Fleury, A.; Alexander, J.

doi:10.1103/physrevc.16.706

Cited by 20 publications

(19 citation statements)

References 23 publications

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“…The statistical decay formalism, as well as the approximation introduced in the GROGI-F code, are well documented in the literature [42, 49,59,60]. We present here only the values of the main parameters used in our calculations.…”

Section: Appendixmentioning

confidence: 98%

Competition between few nucleon emission and?-ray deexcitation for the reaction systems65Cu+87Rb and40Ar+110Pd

et al. 1985

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Both y-ray and neutron emission have been studied for the reaction systems 65Cu(237MeV)+87Rb~t52Dy* and 4~ MeV)+ ax~176 By using a sum spectrometer in coincidence with neutron counters, Ge(Li) or NaI detectors, we have measured the total y-ray energy and the average total y-multiplicity distributions as well as the neutron spectra for various exit channels. These measurements provide strong evidence for thermal equilibrium in reactions involving a small number of emitted neutrons (i.e. 87Rb(65Cu, n or 2n)) at rather high excitation energy (~54MeV). This statistical emission of only a few neutrons is controlled by very strong 7-ray competition: the 7-entry line is found not to be parallel to the yrast line. Instead the energy gap is about 8 MeV for J~27h and rises to at least 13 MeV for J~36h. There are some indications that the main part of the energy from this gap is removed by statistical y-ray cascades. The main features of the experimental data for both entrance channels are well reproduced by statistical model calculations with proper attention to the yrast line position and an adjustement of the dipole y-ray normalization coefficient. It is conceivable that the y-ray enhancement that we introduce may be related to a lack of knowledge of the absolute level densities at high energy and spin, or possibly to the presence of new or additional degrees of freedom that may enter into the competition between neutron and y-ray emission.

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Section: Appendixmentioning

confidence: 98%

Competition between few nucleon emission and?-ray deexcitation for the reaction systems65Cu+87Rb and40Ar+110Pd

et al. 1985

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“…Experimental data for the fission excitation function in Fig. 3 are from [2] (with error bars) and additional points from [18] (without error bars). The dashed lines in Fig.…”

Section: Comparison To Experimentsmentioning

confidence: 99%

“…To test the effectiveness of the model, we performed evaporation calculations for the extensively studied reaction systems 12C+lS2W and 4~ 1~4Sm [2,10,18]. These systems were chosen because the mass of the composite nucleus t94Hg is in a region where various models [19] predict almost identical heights for the s-wave fission barrier, and an appreciable amount of evaporation residues has been experimentally determined.…”

Section: Comparison To Experimentsmentioning

confidence: 99%

Particle-to-fission competition at high excitation energies

Westmeier

Esterlund

1984

Z Physik A

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For application in statistical model evaporation codes, a model is presented which describes the experimental observation of multifold particle emission prior to fission, even from very fissile highly excited composite nuclei. This model is based upon the assumption that collective motion of many nucleons towards the scission point is slow compared to evaporation times for single nucleons. The relative times required for particle evaporation and collective motion towards the scission point are estimated, using as a first-order approximation, the frequencies of the lowest modes of particle vibration and low-frequency fl-qnadrupole vibration, respectively. Comparisons with data for the systems 12C+182W, ~~ ~9F+~S~Ta, and 2~ show good agreement with the model calculations.

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“…4b. Parameters similar to these were selected by Delagrange et al [28] to fit the steep fission excitation function for 12C+lS2W (50<E*<100MeV). In Ref.…”

Section: General Relationship To the Statistical Modelmentioning

confidence: 99%

“…To illustrate this delicacy let us examine three field maps in the E*, J plane for the decay probability resulting from several parametrizations of first step evaporative decay from 194Hg*. (We use the code EMIK, a modification of GROGIF [26], designed to provide emission probabilities and lifetimes by the methods originally described by Grover and Gilat [27] and used by other authors [26,28].) These calculated maps do not change drastically for other members of the evaporation cascade.…”

Section: General Relationship To the Statistical Modelmentioning

confidence: 99%

Anomalous behavior of evaporative H/He from194Hg compound nuclei

et al. 1982

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From measured cross sections for evaporative ~H and 4He, we have unfolded the separate effects of excitation energy (E*) and spin (J) on the decay of 194Hg*. The analysis depends only on Bohr's independence hypothesis and on certain general features of the transmission coefficients for fusion. Evaporation-like emission of 1H and 4He increases rapidly with energy but decreases rather mildly with initial spin. Significant emission occurs even for very high spins where the calculated fission barrier is essentially zero. The equilibrium model for fission-evaporation competition is brought into question for E* > 98 MeV and J ~> 65 h.

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Fission probability calculations for heavy-ion induced reactions

Cited by 20 publications

References 23 publications

Competition between few nucleon emission and?-ray deexcitation for the reaction systems65Cu+87Rb and40Ar+110Pd

Competition between few nucleon emission and?-ray deexcitation for the reaction systems65Cu+87Rb and40Ar+110Pd

Particle-to-fission competition at high excitation energies

Anomalous behavior of evaporative H/He from194Hg compound nuclei

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