[en] In the framework of this thesis the excitation functions of the systems ¹¹⁰Pd + ¹¹⁰Pd and ¹¹⁰Pd + ¹⁰⁴ Ru could be measured. The evaporation-residual-nucleus cross sections is deviating from lighter systems dominated by channels, which arise from evaporation of α particles. In the reaction ¹¹⁰Pd + ¹¹⁰Pd no xn channels were observed. In comparison to other reactions qualitatively a strong fusion hindrance of this system is shown. (orig./HSI)

[en] In parallel to the attempts to synthesize the heaviest nuclei, systematic studies have been made to obtain better understanding of the reaction aspects. Nearly mass-symmetric massive systems combine high Coulomb forces in the entrance channel with evaporation-residue cross sections which are high enough to be easily detectable. With these systems, rather cold compound nuclei can be produced, and even radiative fusion was observed. While one of the most salient features of the fusion of light and medium-heavy systems is the enhanced sub-barrier fusion, the massive systems exhibit a considerable deficit of fusion above the expected potential barrier. The experimental data reveal that this hindrance to fusion is strongly influenced by the nuclear structure of the reaction partners. The high fission competition in the evaporation cascade of fissile excited compound systems as deduced from measured evaporation-residue cross sections is compared with the expectations of the statistical model. Experimental evidence is presented that the increase of the fission barriers due to spherical shell effects in the ground state does not reduce the fission probability in the de-excitation process. A re-examination of the nuclear level density reveals essentially two explanations for this surprising effect: the temperature-induced deformation due to the collective enhancement in the nuclear level density and the mutual support of magicities due to residual neutron-proton interactions which depend on the occupation of the single-particle levels. In contrast to lighter systems, the evaporation residues of the most massive symmetric systems revealed some indication that the fusion and de-excitation processes are not decoupled by the intermediate stage of a compound nucleus but that they overlap in time and influence each other. Several characteristics found in the synthesis of the heaviest elem

[en] A new 2-dimensional position sensitive semiconductor detector was developed. With this detector the correlation between implanted fusion products and their subsequent α decays can be improved. The position resolution of the detector will be described as a function of the position. Measurements with α-particles and a model of the detector will be presented and the results for the correlation technique are demonstrated. (orig.)

[en] Published in summary form only

[en] The fusion of the massive systems ¹¹⁰Pd+¹⁰⁴Ru and ¹¹⁰Pd+¹¹⁰Pd was uniquely identified by observing the α decay of the evaporation residues. The observed distribution of the fusion cross section on the different evaporation-residue channels is in clear contradiction to calculations based on the compound-nucleus model. As a possible explanation the precompound of α particles is proposed. (orig.)

[en] Published in summary form only

[en] Published in summary form only

[en] The neutron-deficient isotopes ²²⁶Np and ²²⁷Np were produced in the bombardment of a 380 μg/cm²²⁰⁹Bi target with ²²Ne projectiles at an incident beam energy of 5.5 MeV/u. They were identified using the α-α time-correlation method. ²²⁶Np was found to decay with E_α = (8044 ± 20) keV and T_1/2 = (31 ± 8) ms. For ²²⁷Np two α-lines were obserbed at (7650 ± 20) keV and (7677 ± 20) keV with a half-life of (510 ± 60) ms. The gas-filled separator NASE installed at GSI Darmstadt was used to separate the evaporation residues in-flight. (orig.)

[en] Cross sections of iridium and platinum isotopes have been measured, which were produced as fragments from ¹⁹⁷Au projectiles interacting with aluminum target nuclei at 1 A GeV. The fragments were identified by a kinematic analysis (ΔE-Bρ - time-of-flight) and by an ion-optical separation at the projectile-fragment separator FRS at GSI. Indications are found for high excitation energies and weak proton-neutron correlations in the peripheral nuclear-collision process. (orig.)

[en] For the compound nucleus ¹⁷⁹Au formed at an excitation energy of 26 MeV in the fusion reaction ⁹⁰Zr+⁸⁹Y, the energy spectra of promptly emitted protons, α particles and γ rays were measured in concidence with the evaporation residues. On the basis of the measured total decay energy, the 1 p and 1 α decay channels were separated from all other evaporation-residue channels. The energy spectra and absolute cross sections, together with previously measured excitation functions for various decay channels, are successfully described by statistical-model calculations with the Monte Carlo code CODEX. (orig.)