Kinetic energy deficit in the symmetric fission of /sup 259/Md. [Light particle emission in /sup 256/Fm fission]
The fragment energies of about 725 coincidence events have now been observed in the spontaneous fission (SF) decay of 105-min /sup 259/Md since its discovery in 1977. The fission of /sup 259/Md is characterized by a symmetric mass distribution, similar to those of /sup 258/Fm and /sup 259/Fm, but with a broad total kinetic energy (anti TKE) distribution which peaks at about 195 MeV, in contrast to those of /sup 258/Fm and /sup 259/Fm, for which the anti TKE is about 240 MeV. This kinetic energy deficit, approx. 40 MeV, has been postulated to be due to the emission of hydrogen-like particles by /sup 259/Md at the scission point in a large fraction of the fissions, leaving the residual fissioning nucleus with 100 protons. The residual nucleus would then be able to divide into two ultrastable tin-like fission fragments, but with less kinetic energy than that observed in the SF of /sup 258/Fm and /sup 259/Fm, because of binding-energy losses and a reduction in the Coulomb repulsion of the major fragments. To test this hypothesis, counter-telescope experiments aimed at detecting and identifying these light particles were performed. In 439 SF events 3 + 3 protons of the appropriate energy were observed, too few to account for the kinetic energy deficit in the fission of /sup 259/Md. There seems to be no explanation for this problem within the framework of current fission theory. These results are discussed along with preliminary measurements of light-particle emission in the SF of /sup 256/Fm. 5 figures.
- Research Organization:
- California Univ., Livermore (USA). Lawrence Livermore National Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6837298
- Report Number(s):
- UCRL-84408; CONF-8009116-1
- Country of Publication:
- United States
- Language:
- English
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Unusually low fragment energies in the symmetric fission of /sup 259/Md
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Related Subjects
A=220 & above
Experimental-- Spontaneous & Induced Fission-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
DATA
DECAY
ENERGY
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FERMIUM 256
FERMIUM ISOTOPES
FISSION
FISSION FRAGMENTS
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
INFORMATION
ISOTOPES
KINETIC ENERGY
KINETICS
MASS NUMBER
MASS SPECTRA
MENDELEVIUM 259
MENDELEVIUM ISOTOPES
NUCLEAR FRAGMENTS
NUCLEAR REACTION KINETICS
NUCLEAR REACTIONS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
RADIOISOTOPES
REACTION KINETICS
SPECTRA
SPONTANEOUS FISSION
TERNARY FISSION