Discovery of /sup 260/Md and the decay properties of /sup 258/Fm, /sup 258m,g/Md, and /sup 259/Md

Conference · Thu Aug 01 00:00:00 EDT 1985

OSTI ID:5309390

Lougheed, R W; Hulet, E K; Dougan, R J; Wild, J F; Dupzyk, R J; Henderson, C M; Moody, K J; Hahn, R L; Suemmerer, K; Bethune, G

We have discovered a new neutron-rich isotope, /sup 260/Md, from /sup 18/O and /sup 22/Ne bombardments of /sup 254/Es. We observed a spontaneous-fission (SF) activity with a 32-day half-life in electromagnetically separated mass-260 fractions from these bombardments and we have measured the mass and kinetic energy distributions of this SF activity. The mass distribution was symmetric with the principal energy peak at 234-MeV total kinetic energy (TKE), similar to previous observations for heavy Fm isotopes. Surprisingly, we also observed a smaller symmetric component with 195-MeV TKE. We interpret these two peaks in the TKE distribution as arising from two types of fission in the same nucleus, or bimodal fission. The observed fission activity may be either from the SF decay of /sup 260/Md or /sup 260/Fm which would arise from electron capture (EC) decay of /sup 260/Md. We have eliminated the possible ..beta../sup -/ decay of /sup 260/Md by measuring ..beta../sup -/-SF time correlations for the decay of /sup 260/Md and we plan to determine if /sup 260/Md decays by EC by measuring time correlations between Fm x-rays and SF events. We also measured properties for heavy Fm and Md isotopes which include: (1) more accurate cross sections for the neutron-rich Md isotopes which we use to predict the production rates of yet undiscovered nuclides; (2) improved half-live measurements for /sup 258m,g/Md and /sup 259/Md; (3) confirmation of the EC decay of /sup 258m/Md by measuring Fm x-rays preceding the SF decay of /sup 258/Fm; and (4) very substantially improved mass and TKE distributions for the SF decay of /sup 258/Fm and /sup 259/Md.

• Research Organization: Lawrence Livermore National Lab., CA (USA); Oak Ridge National Lab., TN (USA); Gesellschaft fuer Schwerionenforschung m.b.H., Darmstadt (Germany, F.R.); Bethune-Cookman Coll., Daytona Beach, FL (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5309390
• Report Number(s): UCRL-93260; CONF-8509147-5; ON: DE85017835
• Resource Relation: Conference: ACTINIDES '85, Aix-en-Provence, France, 1 Sep 1985
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
FERMIUM 258
DECAY
MENDELEVIUM 258
MENDELEVIUM 259
MENDELEVIUM 260
BETA-MINUS DECAY
EINSTEINIUM 254 TARGET
ENERGY SPECTRA
EXPERIMENTAL DATA
HALF-LIFE
MASS SPECTRA
NEON 22 REACTIONS
OXYGEN 18 REACTIONS
SPONTANEOUS FISSION
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
BETA DECAY
CHARGED-PARTICLE REACTIONS
DATA
EVEN-EVEN NUCLEI
FERMIUM ISOTOPES
FISSION
HEAVY ION REACTIONS
HEAVY NUCLEI
INFORMATION
ISOTOPES
MENDELEVIUM ISOTOPES
MICROSEC LIVING RADIOISOTOPES
MINUTES LIVING RADIOISOTOPES
NUCLEAR REACTIONS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
RADIOISOTOPES
SPECTRA
TARGETS
652025* - Nuclear Properties & Reactions
A=220 & above
Experimental- Nuclear Reactions & Scattering- (-1987)
652022 - Nuclear Properties & Reactions
A=220 & above
Experimental- Radioactive Decay- (-1987)