[en] In the present thesis, the shell structure in exotic nuclei has been investigated. The focus of the work was on finding new experimental data in neutron-rich Cr and proton-rich Ca isotopes. The investigation of light Ca isotopes concentrated on the nucleus ³⁶Ca which was produced in a knockout reaction from a radioactive ³⁷Ca beam. For ³⁶Ca, the excitation energy of the first 2⁺ state has been measured for the first time. Furthermore, momentum distributions were analyzed using a Monte-Carlo simulation of the knockout reaction. This analysis yielded the contributions of neutrons from individual orbitals to the total knockout cross section. In principle, these may be used to calculate spectroscopic factors, but such a calculation is hampered by difficulties of present knockout-reaction models in predicting precise single-particle cross sections. The measured branching ratio to the ground and excited states, on the other hand, is close to the predicted value. A remaining difference might be due to emission of protons which cannot be detected with the present experimental setup. Both the branching ratio and the large excitation energy are compatible with a large N=16 gap in ³⁶Ca that leads to relatively pure configurations both in the ground state and the excited 2⁺ state. As a by-product of the experiment, two excitation energies in the T=2 nuclei ³²Ar and ²⁸S have been confirmed, and two γ-ray transitions have been observed for the first time in ³⁷Ca. While the mirror energy differences in the T=2 pairs ³⁶Ca-³⁶S, ³²Ar-³²Si, and ²⁸S-²⁸Mg can be reproduced in shell model calculations using a modified USD interaction, these modifications are not sufficient to explain the mirror energy differences for the pair ³⁷Ca-³⁷Cl. In the heavy Cr isotopes, new experimental evidence for a sub-shell closure at N=32 was found in a measurement of B(E2) values using high-energy Coulomb excitation of radioactive beams. Prior to this experiment, the assumption of a sub-shell closure was based only on systematics of excitation energies of the first 2⁺ states in Cr, Ti, and Ca isotopes. The small B(E2) value for ⁵⁶Cr is in agreement with these indications. Further evidence for a N=32 shell gap has meanwhile been found in the development of B(E2) values in Ti isotopes and the evolution of E(4⁺)/E(2⁺) ratios for Cr and Ti. While the experimental evidence has firmly established a sub-shell closure at N=32, calculations are, at present, not able to reproduce the behavior of the B(E2) values, whereas the evolution of excitation energies is well described. Both results touch the limits of present nuclear structure models: in the Cr isotopes, the B(E2) evolution cannot yet be reproduced, and in the Ca isotopes, a consistent picture of mirror energy differences as well as a successful calculation of cross sections are missing. As a result of this work, new experimental data are available for future improvements of such calculations. (orig.)

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[en] In nuclear physics experiments involving in-flight fragmentation of ions, usually a large number of different nuclei is produced and various detection systems are employed to identify the species event by event, e.g., by measuring their specific energy loss and time of flight. For such cases - not necessarily limited to nuclear physics - where subsets of a large data set can be identified using a small number of measured signals, a software for fast access to varying subsets of such a data set has been developed. The software has been used successfully in the analysis of a one neutron knock-out experiment at GANIL

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[en] The measurement is described of electron mobility in semiconducting plates placed between two cylindrical antennas with diameter d approximately equal to 0.75lambda₀ by means of the microwave Faraday effect. This system makes it possible (i) to measure the Faraday rotation in semiconductina plates of arbitrary transverse dimensions, greater or at least equal to the diameter of dielectric antennas, (ii) to evaluate the unknown value of the charge carrier mobility from the measured rotation in an unbounded solid state plasma slab approximation. The measurement of Faraday rotation in n-type Ge plates is reported. The comparison of the experimental data with the theory shows good agreement. (author)

[en] Particle-γ coincidences from the bombardment of 15 MeV and 32 MeV protons on a ⁴⁶Ti target are utilized to obtain γ-ray spectra as a function of excitation energy for ^44,45,46Ti. The Oslo method has been used to extract simultaneously level density and γ-ray strength functions (γ-SFs). The rich ⁴⁶Ti data set of 110 million events allows analysis of the coincidence data for many independent data sets. As expected, the results are consistent with one common level density. A method to study the evolution of the deduced γ-SFs as a function of excitation energy will be described. The γ-SFs are found to display strong variations for different initial and final excitation energies if transitions to the lowest states are involved. The differences in the γ-SFs can be explained as a consequence of Porter-Thomas fluctuations of individual intensities, and shows that this energy region cannot be used for determination of the universal γ-RSF. Even though, the deduced γ-SFs based on transitions within the quasi-continuum still indicate that the decay is governed by a universal γ-SF

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[en] The first excited 2⁺ states in ^54,56,58Cr have been populated by relativistic Coulomb excitation using the FRS-RISING setup at GSI. The Cr ions were produced by fragmentation of a ⁸⁶Kr beam on a primary Be target and separated by the FRS. The ion beams impinged on a thick secondary Au target at an energy of around 135 A MeV. Gamma-rays were observed by the Ge cluster detectors of the RISING setup and stored in coincidence with particle and position signals from a set of tracking detectors. The steps of the analysis and spectra showing the 2⁺ → 0⁺ transitions are presented. (author)