Neutron emission as a probe of fusion-fission and quasifission dynamics

Journal Article · Sun Mar 01 00:00:00 EST 1992 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.45.1229· OSTI ID:7205933

Hinde, D J ^[1]; Hilscher, D; Rossner, H; Gebauer, B; Lehmann, M; Wilpert, M ^[2]

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1. Hahn-Meitner-Institut Berlin, D-1000 Berlin 39 (Germany) Department of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University, GPO Box 4, Canberra, ACT 2601 (Australia)
2. Hahn-Meitner-Institut Berlin, D-1000 Berlin 39 (Germany)

Pre-scission and post-scission neutron yields have been measured as a function of projectile mass, compound nucleus fissility, and fission mass split and total kinetic energy (TKE) for 27 fusion-fission and quasifission reactions induced by beams of {sup 16,18}O, {sup 40}Ar, and {sup 64}Ni. A new method of interpretation of experimental pre-scission neutron multiplicities {nu}{sub pre} and mean kinetic energies {var epsilon}{sub {nu}} allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35{plus minus}15){times}10{sup {minus}21} s for symmetric fission. All reactions show that {nu}{sub pre} falls quite rapidly with increasing mass asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass asymmetry. For quasifission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass asymmetry, but that the time scale is virtually independent of mass asymmetry. It is concluded that for fusion-fission there is no dependence of {nu}{sub pre} on TKE, while for {sup 64}Ni-induced quasifission reactions, a strong increase of {nu}{sub pre} with decreasing TKE is observed. This is probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data.

• OSTI ID: 7205933
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Vol. 45:3; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ARGON 40 REACTIONS
FISSION
HEAVY ION REACTIONS
NICKEL 64 REACTIONS
OXYGEN 16 REACTIONS
OXYGEN 18 REACTIONS
URANIUM 238 TARGET
COMPOUND-NUCLEUS REACTIONS
EXPERIMENTAL DATA
FISSION SPECTRA
MEV RANGE 100-1000
CHARGED-PARTICLE REACTIONS
DATA
ENERGY RANGE
INFORMATION
MEV RANGE
NUCLEAR REACTIONS
NUMERICAL DATA
SPECTRA
TARGETS
663450* - Heavy-Ion-Induced Reactions & Scattering- (1992-)