Correlations between fission fragments and light charged-particles in the reaction20Ne+197Au at 13 MeV/nucleon

Rivet, M. F.; Gatty, B.; Guillemot, H.; Borderie, B.; Bimbot, R.; Forest, I.; Galin, J.; Guerreau, D.; Lefórt, M.; Tarrago, X.; Tamain, B.; Novicki, L.

doi:10.1007/bf01421298

Cited by 17 publications

(4 citation statements)

References 26 publications

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“…For reactions of 3t5 MeV 160 and 340MeV 4~ with 238U, similar observations have been made via measurements of 4He production in coincidence with fission fragments of known fold angle [34,38,96 and references therein]. Production of #He in the backward hemisphere was found to be predominantly associated with essentially full momentum transfer to the fissile nucleus, The reaction 265MeV 2~ has also been studied by Rivet et al [46] who arrive at similar conclusions. Several studies of similar reactions have reported that forward-angle inclusive spectra can be parameterized by an isotropic emission source moving at one-half to two-thirds of the projectile velocity vp.…”

Section: Experimental Techniquessupporting

confidence: 63%

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Fission and emission of H and He in the reactions of 215 MeV16O with181Ta,208Pb and238U

et al. 1984

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The reactions of 215 MeV 160 with 12C, lSlTa, 2~ and 238U have been studied. Inclusive measurements for 4He emission are given from each target, and for fission and 1"2'3H from Ta, Pb and U. For H/He a high-energy, forward-peaked component is observed with characteristics similar to those reported by others. At backward angles a low-energy, nearly-isotropic component is also observed for 4He that cannot be accounted for by emission from fully accelerated fission products. The spectral shapes for this evaporative component are compared with statistical model calculations, and information is obtained concerning the effective barriers to emission. For the reactions of 16.O with 12C, complete fusion seems to be overwhelmed by incomplete fusion. Fission angular distributions and cross sections are also presented and discussed.

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Section: Experimental Techniquessupporting

confidence: 63%

“…No. 1, F-91406 Orsay, France ration of fission-like fragments [38,46,[63][64][65][95][96][97]. The nearly isotropic component is particularly interesting for heavy nuclei as it offers a possible probe of the time evolution of the composite nucleus in its course toward fission-like breakup [64,[96][97][98].…”

Section: Introductionmentioning

confidence: 98%

Fission and emission of H and He in the reactions of 215 MeV16O with181Ta,208Pb and238U

et al. 1984

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“…The first clue to such a comportment can even be found in light particle induced reactions on heavy targets [1,4]. Extensive studies of charged particle emission in heavy-ion reactions [7][8][9][10][11][12][13][14][15][16][17]19] have fully confirmed the existence of this anomalous type of evaporation and precised its characteristics as functions of excitation energy and spin, see e.g. Ref.…”

Section: Introductionmentioning

confidence: 82%

Dynamical decay of nuclei at high temperature: Competition between particle emission and fission decay

Delagrange

Grégoire

Scheuter

et al. 1986

Z. Physik A - Atomic Nuclei

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“…In principle, the simultaneous measurement of the fission fragment folding angle in case of fissile heavy residues may provide analogue information. However, an experiment of this type by Rivet et al [31] on the same reaction as studied here did not cover the interesting range of e-particle emission angles below 50 ~ For the system 310MeV 160AFZ38u studied by…”

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confidence: 99%

Two different sources of fast forward-emittedα-particles in heavy-ion reactions

Homeyer¹,

Jahnke²,

Ingold³

et al. 1983

Z Physik A

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For the reaction 290 MeV 2~197Au the number of neutrons emitted in coincidence with e-particles is used to discriminate between two equally important but qualitatively different mechanisms for the emission of fast e-particles. They are connected with low and high inelasticity, respectively, and the resulting e-particles differ in mean velocity and velocity distribution.All the time since 1961 when Britt and Quinton [1] for the first time observed the emission of fast forward-directed e-particles in heavy-ion collisions at energies around 10 MeV/nucleon, their origin has been the subject of much theoretical and experimental effort. The explanations proposed range from preequilibrium emission [2], emission from a hot spot [3,4], a hot moving source [5,7] or a fireball, over sequential projectile decay (sequential breakup) [8-12] to projectile fragmentation (direct breakup) [13][14][15], uncorrelated emission 1-17-19], and incomplete fusion [20][21][22] or massive transfer [23,24]. In all these investigations, only one mechanism was considered explicitly, a possible second mechanism appearing only sometimes through an unexplained remainder in the inclusive cross sections [10,25]. However, assessing all existing evidence, one has to anticipate the virtual coexistence of (at least) two mechanisms in a heavy-ion reaction above 10 MeV/ nucleon: the sequential decay of excited projectilelike fragme~.ts as a more familiar process, and besides that a type of fast, non-equilibrium emission. Here we present for the representative case of the 290MeV 2~ system an explicit experimental decomposition of inclusive e-particle cross sections into two components resulting from different production modes. The decomposition was achieved by counting with high efficiency the neutrons emitted simultaneously with each c~-particle. The neutron number is a measure of the energy converted into internal excitation. This method was previously applied [26] to projectile-like fragments from the same system. There it allowed to discriminate between projectile residues the formation of which implied the transfer of an e-particle to the target, and the same residues emerging after emission of an e-particle. In that experiment results were also obtained for e-particles which shall be discussed here. Some experimental details are given in [26]. The previous information is resumed in Fig. 1. It shows the inclusive e-particle spectrum measured [25] at 22 ~ which is characterized by the well known intense high-energy contribution superimposed onto the evaporation component. The latter is derived from a measurement at backward angles using the symmetry of its c.m.s, angular distribution about 90 ~ A second component shown is the calculated contribution of e-particles accompanied by a projectile-like fragment, i.e. the contribution of projectile break-up. The calculation is based on a measurement of in-plane coincidences [9] of e-particles with projectile-like fragments. All (or at least about 95 ~) of these coincidences were due to the sequential edecay ...

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Correlations between fission fragments and light charged-particles in the reaction20Ne+197Au at 13 MeV/nucleon

Cited by 17 publications

References 26 publications

Fission and emission of H and He in the reactions of 215 MeV16O with181Ta,208Pb and238U

Fission and emission of H and He in the reactions of 215 MeV16O with181Ta,208Pb and238U

Dynamical decay of nuclei at high temperature: Competition between particle emission and fission decay

Two different sources of fast forward-emittedα-particles in heavy-ion reactions

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