Neutrons in coincidence with fission of {sup 238}U induced by stopped antiprotons

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Physical Review, C

DOI:https://doi.org/10.1103/PhysRevC.55.2965· OSTI ID:509097

Schmid, W; von Egidy, T; Hartmann, F J; Hoffmann, J; Schmid, S ^[1]; Hilscher, D; Polster, D; Rossner, H ^[2]; Iljinov, A S; Mebel, M V; Ivanov, D I; Nedorezov, V G; Sudov, A S ^[3]; Machner, H; Plendl, H S ^[4]; Eades, J; Neumaier, S ^[5]

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1. Physik-Department, Technische Universitaet Muenchen, D-85748 Garching (Germany)
2. Hahn-Meitner-Institut-Berlin, D-14109 Berlin (Germany)
3. Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow (Russia)
4. KFA Juelich, D-52425 Juelich (Germany)
5. CERN, 1211-Geneva 21 (Switzerland)

Neutron multiplicities after antiproton-induced fission have been determined as a function of the total mass of the fission fragments. Pre- and postscission neutron multiplicities of the reaction {bar p}+{sup 238}U have been deduced using the moving-source parametrization of the neutron energy spectra by Maxwellian distributions. A postscission multiplicity of 6.3(6) neutrons out of 20.0(10) in total emitted neutrons in fission indicates that fission is a rather slow process. The increase of the evaporative prescission neutron multiplicity is about 80{percent} of the total increase of evaporative neutrons as a measure of excitation energy. The postscission multiplicity gets only 20{percent} of the total increase, thus indicating that the nucleus has only a moderate excitation energy at the moment of scission. The results are compared with standard cascade-evaporation calculations predicting a much lower number of evaporated prescission neutrons as the experiment shows. This is a strong indication of the importance of dissipative effects in the fission process. Application of dissipative effects like a saddle-to-scission delay time and nuclear viscosity in the model calculation describes the experimental results much better. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 509097
• Journal Information: Physical Review, C, Journal Name: Physical Review, C Journal Issue: 6 Vol. 55; ISSN PRVCAN; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANTIPROTON REACTIONS
ENERGY SPECTRA
EVAPORATION MODEL
EXCITATION
FISSION
FISSION FRAGMENTS
MASS
MULTIPLICITY
NEUTRON EMISSION
NEUTRONS
URANIUM 238 TARGET
VISCOSITY