[en] The vacuum polarization contribution of order α(Zα)ⁿ with n≥3 on electron binding energies has been calculated following the prescription of Wichmann and Kroll. The numerical techniques for the evaluation of the vacuum polarization charge density are discussed. Results are presented for atoms with Z=73, 82 and 170, respectively. (orig.)

[en] Quantum electrodynamical corrections in hydrogen-like atoms are reviewed. In particular the Wichmann-Kroll contribution to the total vacuum polarization charge density is investigated. Limits for precision tests of quantum electrodynamics in strong Coulomb fields are given. A significant parity violation effect in helium-like uranium is pointed out. (orig.)

[en] We investigate field-theoretical corrections, such as vacuum polarization and self energy to study their influence on strongly bound electrons in heavy and superheavy atoms. In critical fields (Z≅170) for spontaneous e⁺e^- pair creation the coupling constant of the external field Zα exceeds 1 thereby preventing the ordinary perturbative approach of quantum electrodynamical correction which employs an expansion in Zα. For heavy and superheavy elements radiative corrections have to be treated to all orders in Zα. The dominant effect is provided by the Uehling contribution being visualized by the first diagram on the right hand side. It is linear in the external field and thus of order α(Zα). (orig./HSI)

[en] Selected topics are presented which have been extensively discussed at the parallel conference 'Physics of Strong Fields' in Maratea (Italy). Special emphasis is laid on the origin of puzzling peak structures in positron spectra being observed in collisions of very heavy ions. Additionally it is demonstrated that the spectral distribution of high-energy electrons and positrons may serve as an accurate atomic clock to determine the time delay associated with deep-inelastic nuclear reactions. (orig.)

[en] Contributions to the electron Lamb shift in highly charged ions are summarized. Recent theoretical developments as well as current experimental results are considered. Special emphasis is laid on higher-order vacuum polarization corrections as well as on the nuclear size effect on the electron self energy. (orig.). 5 figs

[en] We explicitly construct normalized solutions of the Klein-Gordon equation for various types of attractive potentials. Our computed binding energies of several short- and long-range potentials are compared with results published by different authors. Special emphasis is laid on the determination of critical potential strengths, i.e. the onset of spontaneous pair creation of spin-0 particles. In the vicinity of these critical values the single-particle interpretation breaks down. The phenomenon of simultaneous particle and antiparticle binding in a short-range potential is investigated. (orig.)

[en] Relativistic wave packets are explicitly constructed and exploited in calculations of ionization phenomena. Coupling matrix elements between bound states and wave packets are evaluated for radiative transitions as well as for electron excitation processes. The momentum distribution of bound state wavefunctions in superheavy systems is presented. (orig.)

[en] We calculate the energy levels of K- and L-shell electrons in lead, uranium, fermium and in the superheavy system Z = 169 taking into account various nuclear charge distributions and the muonic vacuum polarization. (orig.)

[en] The Dirac equation is solved for various types of scalar potentials. Energy eigenvalues and normalized bound-state wave functions are calculated analytically for a scalar 1/r-potential as well as for a mixed scalar and Coulomb 1/r-potential. Also continuum wave functions for positive and negative energies are derived. Similarly, we investigate the solutions of the Dirac equation for a scalar square-well potential. Relativistic wave functions for scalar Yukawa and exponential potentials are determined numerically. Finally, we also discuss solutions of the Dirac equation for scalar linear and quadratic potentials which are frequently used to simulate quark confinement. (orig.). 18 figs

[en] Employing the semiclassical approximation we calculate within the coupled-state formalism the ionization probability in antiproton-hydrogen (anti p+H) collisions. In particular we investigate the adiabatic ionization at the distance of closest approach in almost central collisions. Striking differences in the electron excitation probability compared with proton-hydrogen (p+H) collisions are predicted. (orig.)