Neutrons in coincidence with fission of {sup 238}U induced by stopped antiprotons
- Physik-Department, Technische Universitaet Muenchen, D-85748 Garching (Germany)
- Hahn-Meitner-Institut-Berlin, D-14109 Berlin (Germany)
- Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow (Russia)
- KFA Juelich, D-52425 Juelich (Germany)
- 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, Vol. 55, Issue 6; Other Information: PBD: Jun 1997
- Country of Publication:
- United States
- Language:
- English
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