Neutron emission in central heavy-ion collisions of /sup 165/Ho + /sup 20/Ne at 11, 14. 6, and 20. 1 MeV/nucleon

Journal Article · Fri Jul 01 04:00:00 EDT 1983 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.28.252· OSTI ID:5908990

Holub, E; Hilscher, D; Ingold, G; Jahnke, U; Orf, H; Rossner, H

The neutron emission from fusionlike reactions leading to evaporation residues and fission fragments was measured in the reaction /sup 165/Ho+/sup 20/Ne at 220, 292, and 402 MeV /sup 20/Ne bombarding energies. Preequilibrium high-energy neutrons having up to twice the beam velocity were observed. The multiplicity of these neutrons increases with the bombarding energy from 0.4 to 2.3. This corresponds to 5 to 15 % of the total number of neutrons emitted per fusionlike event. The measured energy spectra of the highly energetic neutrons cannot be described with the Fermi-jet mechanism (one body promptly emitted particles), especially at angles larger than 35/sup 0/. Reasonable agreement with the modified Harp-Miller-Berne model can be obtained. In that case, however, it is necessary to treat the initial degree of freedom as a parameter which increases with bombarding energy from 20 to 28. The evaporative component in the energy spectra of fusion-fission events was used to deduce that the number of prefission neutrons is 5.6 +- 0.5, 5.8 +- 0.5, and 5.3 +- 1.0 at bombarding energies of 220, 292, and 402 MeV, respectively, whereas the statistical model predicts a maximum number of 1.6 to 2.0 prefission neutrons. Although no conclusive explanation can be given for the unexpectedly large multiple chance fission probability, it is suggested that most of the additional prefission neutrons are emitted during the transition from saddle to scission.

• Research Organization: Hahn-Meitner-Institut fuer Kernforschung Berlin, 1000 Berlin 39, Federal Republic of Germany
• OSTI ID: 5908990
• Journal Information: Phys. Rev. C; (United States), Journal Name: Phys. Rev. C; (United States) Vol. 28:1; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

651825* -- Nuclear Properties & Reactions
A=150-189
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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR DISTRIBUTION
CHARGED-PARTICLE REACTIONS
CROSS SECTIONS
DISTRIBUTION
EMISSION
ENERGY RANGE
ENERGY SPECTRA
EVAPORATION MODEL
FISSION
FUSION REACTIONS
HEAVY ION REACTIONS
HOLMIUM 165 TARGET
MATHEMATICAL MODELS
MEV RANGE
MEV RANGE 100-1000
MULTIPLICITY
NEON 20 REACTIONS
NEUTRON EMISSION
NUCLEAR MODELS
NUCLEAR REACTIONS
SPECTRA
TARGETS