Time delays in heavy-ion-induced fission of medium-Z nuclei, measured by crystal blocking
- Aarhus University
- University of Aarhus, Denmark
- Universite de Montreal
- FLNR-JINR, Russia
- ORNL
- University of Bologna
Time delays in fission induced by bombardment of Mo with 170- and 180-MeV {sup 32}S, 225- and 240-MeV {sup 48}Ti, and 300-MeV {sup 58}Ni have been measured by observation of crystal blocking of fission fragments. In contrast to earlier measurements with a W target, the results are consistent with fission of a compound nucleus in competition with mainly neutron emission. Most of the fissions happen on a time scale much shorter than attoseconds but there is a significant component of fission with much longer lifetimes. The measurements are reproduced with a standard statistical model, including a Kramers correction to fission widths from the viscosity of hot nuclear matter. These new results support the interpretation of our earlier measurements with a W target, which indicate that there is a transition in heavy-ion-induced fission at large atomic number and mass, from multichance fission in the standard Bohr-Wheeler picture to fission without formation of a compound nucleus. The process is slowed down by nuclear viscosity, with measured delays of order attoseconds.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Holifield Radioactive Ion Beam Facility (HRIBF)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1038808
- Journal Information:
- Physical Review, C (Nuclear Physics), Vol. 85, Issue 4; ISSN 0556-2813
- Country of Publication:
- United States
- Language:
- English
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