Spontaneous fission of rutherfordium isotopes

Journal Article · Wed May 01 00:00:00 EDT 1985 · Phys. Rev. C; (United States)

DOI:https://doi.org/10.1103/PhysRevC.31.1801· OSTI ID:5753955

Somerville, L P; Nurmia, M J; Nitschke, J M; Ghiorso, A; Hulet, E K; Lougheed, R W

We have found several new spontaneous fission (SF) activities and suggested assignments for some of them to rutherfordium (element 104) isotopes. Their half-lives and production cross sections have been measured by collecting recoils on a moving nickel or steel tape and transporting them past stationary mica track detectors at known velocities. The following tentative assignments are based on several cross bombardments and comparisons between experimental and calculated production cross sections: /sup 256/Rf(9 +- 2 ms), /sup 257/Rf(3.8 +- 0.8 s, 14 +- 9% SF), /sup 258/Rf(13 +- 3 ms), /sup 259/Rf(3.4 +- 1.7 s, 9 +- 3% SF), /sup 260/Rf(21 +- 1 ms), and /sup 262/Rf(47 +- 5 ms). Presently we are unable to assign several other new spontaneous fission activities with half-lives of approx.15 ms, approx.22 ms, approx.100 ms (Z<104), approx.1.6 s, approx.5 s, approx.5 s, approx.30 s, and approx.47 s. Contrary to other observations, we have not found any indication for an 80-ms spontaneous fission activity, earlier credited to the spontaneous fission decay of /sup 260/Rf, in reactions in which we expected to produce this isotope. Our measurements support a shift in the spontaneous fission half-life systematics at element 104, first proposed by Flerov and Oganessian et al. and later predicted by Randrup et al. and Baran et al. and attributed to the disappearance of the second hump of the double-humped fission barrier and a weakening of the 152-neutron subshell.

• Research Organization: University of California, Lawrence Berkeley Laboratory, Berkeley, California 94720
• OSTI ID: 5753955
• Journal Information: Phys. Rev. C; (United States), Vol. 31:5
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ELEMENT 104
SPONTANEOUS FISSION
COULOMB FIELD
CROSS SECTIONS
HALF-LIFE
NEUTRONS
RECOILS
SHELL MODELS
BARYONS
DECAY
ELECTRIC FIELDS
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FISSION
HADRONS
MATHEMATICAL MODELS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEONS
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
652026* - Nuclear Properties &amp; Reactions
A=220 &amp; above
Experimental- Spontaneous &amp; Induced Fission- (-1987)