Evidence for bimodal fission in the heaviest elements
We have measured the mass and kinetic-energy partitioning in the spontaneous fission of five heavy nuclides: /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, and /sup 260/(104). Each was produced by heavy-ion reactions with either /sup 248/Cm, /sup 249/Bk, or /sup 254/Es targets. Energies of correlated fragments from the isotopes with millisecond half lives, /sup 258/No and /sup 260/(104), were measured on-line by a special rotating-wheel instrument, while the others were determined off-line after mass separation. All fissioned with mass distributions that were symmetric. Total-kinetic-energy distributions peaked near either 200 or 235 MeV. Surprisingly, because only a single Gaussian energy distribution had been observed previously in actinide fission, these energy distributions were skewed upward or downward from the peak in each case, except for /sup 260/(104), indicating a composite of two energy distributions. We were able to fit accurately two Gaussian curves to the gross energy distributions from the four remaining nuclides. From the multiple TKE distributions and the shapes of the mass distributions, we conclude that there is a low-energy fission component with liquid-drop characteristics which is admixed with a much higher-energy component due to closed fragment shells. We now have further evidence for this conclusion from measurements of the neutron multiplicity in the spontaneous fission of /sup 260/Md.
- Research Organization:
- University of California, Lawrence Livermore National Laboratory, Livermore, CA 94550
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5401148
- Report Number(s):
- CONF-870970-; TRN: 88-012619
- Journal Information:
- AIP Conf. Proc.; (United States), Vol. 164:1; Conference: 5. international conference on nuclei far from stability, Lake Rosseau, Canada, 14 Sep 1987
- Country of Publication:
- United States
- Language:
- English
Similar Records
Bimodal fission
Spontaneous fission properties of sup 258 Fm, sup 259 Md, sup 260 Md, sup 258 No, and sup 260 (104): Bimodal fission
Related Subjects
BERKELIUM 249 TARGET
NITROGEN 15 REACTIONS
CARBON 13 REACTIONS
HEAVY ION FUSION REACTIONS
CURIUM 248 TARGET
ELEMENT 104
SPONTANEOUS FISSION
FERMIUM 258
MENDELEVIUM ISOTOPES
NOBELIUM 258
ENERGY SPECTRA
EXPERIMENTAL DATA
HEAVY NUCLEI
MASS DISTRIBUTION
MEV RANGE 10-100
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
CHARGED-PARTICLE REACTIONS
DATA
DECAY
DISTRIBUTION
ELEMENTS
ENERGY RANGE
EVEN-EVEN NUCLEI
FERMIUM ISOTOPES
FISSION
HEAVY ION REACTIONS
INFORMATION
ISOTOPES
MEV RANGE
MICROSEC LIVING RADIOISOTOPES
NOBELIUM ISOTOPES
NUCLEAR REACTIONS
NUCLEI
NUMERICAL DATA
RADIOISOTOPES
SPATIAL DISTRIBUTION
SPECTRA
TARGETS
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
652020* - Nuclear Properties & Reactions
A=220 & above
Experimental