Abstract
Evaporation residue cross sections have been measured in reactions40Ar +140Hf,181Ta,182W,184W,natRe at bombarding energiesE/A=(5.5–6.3) MeV/u. The cross sections do not decrease with increasing nuclear temperature, as expected from statistical model calculations. Rather they are found to be roughly constant. This behavior is predominantly affected by an enhanced emission probability of charged particles. Influence of a ‘fission delay’, which is expected atE x>60 MeV from measurements of pre- and post-scission neutrons, on thexn- cross sections has been observed at excitation energiesE x>90 MeV. The possibility to produce transfermium isotopes in ‘hot fusion’ reactions has been investigated in an irradiation of232Th with40Ar. Upper limits of 10 nb for evaporation residues were obtained.
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The authors express their gratitude to Th. Brohm and J. Weckenmann for their assistance during the experiment.
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Heßberger, F.P., Ninov, V. & Ackermann, D. Evaporation residues from heavy (Z=90–93) compound nuclei at excitation energies of Ex ≃ (75–110) MeV. Z. Physik A - Hadrons and Nuclei 343, 301–307 (1992). https://doi.org/10.1007/BF01291529
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DOI: https://doi.org/10.1007/BF01291529