The new isotopes258105,257105,254Lr and253Lr
Abstract
Evaporation residues from the heavy-ion fusion reaction50Ti on209Bi were investigated. They were separated from the projectile beam by the velocity filter SHIP and identified after implantation into an array of position-sensitive surface-barrier detectors by analyzing their α-decay chains. Spontaneous fission was also observed. Four new α emitters,258105 (T1/2=4.4{-0.6/+0.9}s),257105 (T1/2= 1.4{-0.3/+0.6}s),254Lr ( T 1/2= 13{-2/+3}s), and253Lr ( T 1/2=1.3{-0.3/+0.6}s) could be identified. For the isotope257105 we obtained a spontaneous-fission branch of about 20%. A spontaneous-fission activity with a halflife comparable to that for the α decay of258105 was explained as fission of258104, formed by electron capture from258105. An excitation function for evaporation-residue production was measured for bombarding energies in the range of E CM=184.4 MeV to E CM=196.6 MeV. Nearly all evaporation residues we observed, could be attributed to the 1n and 2n deexcitation channels. The maximum cross sections were σ(1n)=c/2.9±0.3) nbarn, and σ(2n)=c/2.1±0.8) nbarn, respectively. We could measure the total kinetic energy of the fission fragments of258104 to be TKE=(220±15) MeV, a value that fits into empirical systematics based on a Z 2/ A 1/3 dependence.
- Publication:
-
Zeitschrift fur Physik A Hadrons and Nuclei
- Pub Date:
- December 1985
- DOI:
- 10.1007/BF01415134
- Bibcode:
- 1985ZPhyA.322..557H
- Keywords:
-
- 23.60.+e;
- 25.85. Ca;
- 25.70. Jj;
- 27.90.+b