The new isotopes258 105,257 105,254 Lr and253 Lr
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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 theirα-decay chains. Spontaneous fission was also observed.
Four newα 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 theα 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 ofE CM=184.4 MeV toE CM=196.6 MeV. Nearly all evaporation residues we observed, could be attributed to the 1n and 2n deexcitation channels. The maximum cross sections wereσ(1n)=c/2.9±0.3) nbarn, andσ(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 aZ 2/A 1/3 dependence.
- The new isotopes258105,257105,254Lr and253Lr
Zeitschrift für Physik A Atoms and Nuclei
Volume 322, Issue 4 , pp 557-566
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- Author Affiliations
- 1. Gesellschaft für Schwerionenforschung mbH, Darmstadt, Germany
- 2. Tata Institute, Bombay, India
- 3. Porsche AG, D-7251, Weissach, Germany
- 4. II. Physikalisches Institut, Universität Gießen, Germany
- 6. Institut für Kernphysik, Technische Hochschule Darmstadt, Germany