The integral production probability of atomic positrons associated with elastic heavy ion collisions at beam energies from 5.9 to 10 MeV/u has been investigated as a function of the characteristic collision time t̂ and with respect to its dependence on the combined nuclear charge Zunited. Recent data from the systems Pb+Pb at 8.6 MeV/u and Pb+U at 8.4 MeV/u exhibit deviations from coupled-channels calculations: The experimental yield increases stronger towards shorter collision times than predicted.

The \ensuremath{\delta}-electron spectra from dissipative reactions of the collision systems Pb+U and Pb+Pb show the influence of large nuclear contact with increasing Q value. An analysis independent of nuclear models allows us to determine the trajectories of the collisions. Comparison with the reaction model of Schmidt, Toneev, and Wolschin and the one of Feldmeier is made. The applicability of \ensuremath{\delta}-electron spectroscopy in lighter systems is discussed.

The δ-electron spectra from binary dissipative PbPb collisions at 8.6 MeV/u incident energy exhibit the influence of an interference pattern due to time delay caused by nuclear contact. A model-independent analysis of these δ-electron spectra is developed to yield the mean trajectories of the colliding nuclei.

A new type of magnetic transport system, the Tori spectrometer, was constructed to measure positrons and electrons simultaneously. Via inhomogeneous toroidal magnetic fields the two charges are spatially separated and transported to different energy-analysing Si(Li) detectors. By means of a magnetic mirror a high positron transmission of about 70% is achieved while electrons are suppressed by about 104. In the particular application for in-beam operation two gas counters for kinematical coincidences are included.

A new magnetic transport system, the Tori spectrometer, which is able to measure positrons and electrons simultaneously, has been used to study the dynamics of collisions between very heavy ions via their influence on the positron and δ-electron spectra. While these spectra obtained in coincidence to elastic scattering agree well with theory based on pure Rutherford trajectories, those observed in coincidence to dissipative collisions can only be described by calculations taking into account a time delay in the collision process. A quantitative analysis gives an estimation for the nuclear contact time in the U + U collision.

The groundstate and a negative parity band of222Th have been observed in the208Pb (180, 4n)222Th reaction by conversion electron and γ-ray spectroscopy identifying the evaporation residues in a recoil separator. The de-excitation pattern is characterized by strong El transitions interconnecting the levels of alternating parity. The yrast levels may be interpreted as a molecularcluster band.

Positron and $\ensuremath{\delta}$-ray spectra have been measured in coincidence with quasielastic scattered particles and fission fragments from the bombardment of Pd, U, and Cm targets with U beams of energies between 5.9 and 8.4 MeV/u. For collisions leading to a fission reaction, the atomic positron and $\ensuremath{\delta}$-ray spectra fall off more steeply at high energies than expected from calculations based on pure Rutherford trajectories. A quantitative analysis of this effect is in accord with a nuclear contact time of about ${10}^{\ensuremath{-}21}$ s.