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A theoretical study of the K-shell ionization of hydrogen-like ions, colliding with bare nuclei, is performed within the framework of the time-dependent Dirac equation. Special emphasis is placed on the ionization probability that is investigated as a function of impact parameter, collision energy and nuclear charge. To evaluate this probability in a wide range of collisional parameters we propose a simple analytical expression for the transition amplitude. This expression contains three fitting parameters that are determined from the numerical calculations, based on the adiabatic approximation. In contrast to previous studies, our analytical expression for the transition amplitude and ionization probability accounts for the full multipole expansion of the two-center potential and allows accurate description of nonsymmetric collisions of nuclei with different atomic numbers, $Z_1 \neq Z_2$. The calculations performed for both symmetric and asymmetric collisions indicate that the ionization probability is reduced when the difference between the atomic numbers of ions increases., Comment: 8 pages, 6 figures

The probability of photoionization of a heavy hydrogen like ion is calculated within the relativistic perturbation theory. The Coulomb potential of a heavy nucleus is taken into account accurately by usage of the corresponding solutions of the Dirac equation. The obtained probability is compared with both nonrelativistic limit and with nonperturbative results based on the numerical solution of the time-dependent Dirac equation. Suppression of ionization is observed in the secondary ionization channel at photon frequency of about $\hbar\omega \approx mc^2$., Comment: 15 pages, 5 figures

The ionization of a hydrogen-like heavy ion by impact of a charged projectile under simultaneous irradiation by a short laser pulse is investigated within the non-perturbative approach, based on numerical solutions of the time-dependent Dirac equation. Special emphasis is placed on the question of whether the laser- and impact-ionization channels interfere with each other, and how this intereference affects the ionization probability. To answer this question we performed detailed calculations for the laser-assisted collisions between hydrogen-like $Pb^{81+}$ and alpha particles. The results of the calculations clearly indicate that for the experimentally relevant set of (collision and laser) parameters, the interference contribution can reach 10% and can be easily controlled by varying the laser frequency., Comment: 9 pages, 10 figures

The monograph considers resonance and polarization effects in quantum electrodynamics processes that take place in a strong external magnetic field. A method for analyzing spin-polarization effects has been developed. The factorization of process cross sections in resonant conditions and the representation of these cross sections in the form of Breit-Wigner are considered. The possibility of testing these effects in modern international projects to test quantum electrodynamics in strong fields is shown., Comment: 283 pages, 24 figures, monograph

The formation of vortex structures at reflection of electron beam from the double layer of the Jupiter ionosphere is investigated in this paper. And also the influence of these vortex structures on the formation of dense upward electron fluxes, accelerated by the double layer potential along the Io flux tube is studied. Then a phase transition to the cyclotron superradiance mode becomes possible for these electrons. The conditions of the vortex perturbations formation are considered. The nonlinear equation is found that describes the vortex dynamics of electrons and its consequences are studied., Comment: 7 pages, 2 figures, accepted for publication in Ukr. J. Phys

The effect of vacuum birefringence in a magnetic field generated by a laser-driven capacitor-coil generator as well as in field of an electromagnetic wave in a radioguide has been theoretically considered. The resulting ellipticity of a linearly polarized laser beam propagating in the considered field configuration is calculated. The obtained results are compared to the parameters of the PVLAS experiment which aims to observe the effect of magnetic vacuum birefringence experimentally., Comment: 7 pages, 7 figures

We consider the resonant generation of an electron-positron pair by two polarized photons to arbitrarily low Landau levels. The resonance occurs when the energy of one photon exceeds the one-photon generation threshold, and the energy of the other photon is multiple to the spacing between the levels. The cross section of the process is determined taking into account the spins of particles. The order of magnitude of the cross section is the highest when the magnetic moments of the particles are oriented along the magnetic field., Comment: 5 pages, 3 figures

In the present work one- and two-photon pair production in a subcritical magnetic field have been considered. Two-photon production has been studied in the resonant case, when the cross section considerably increases compared to the nonresonant case. While one-photon pair production is considered to be the main mechanism of plasma generation in a pulsar magnetosphere, we suggest the existence of another one, which is resonant two-photon production process., Comment: 5 pages, 2 figures

The resonant process of electron-positron pairproduction by an electron in a subcritical magnetic field has been studied when the pair is produced to exited Landau levels. The spin dependency of the process rate has been analyzed. In the spin state with the greatest rate the virtual photon is emitted with a flip of electron spin. This behavior is not suppressed for radiative transitions from a relativistic initial state to low energy levels., Comment: 4 pages, 1 figure

The process of electron-positron pair production by a photon with subsequent annihilation to a single photon in a strong magnetic field has been studied. The general amplitude has been calculated and the process rate have been found in the low Landau levels approximation (resonant and nonresonant cases). The comparison of resonant and nonresonant cases shows a significant excess of the resonant rate. The polarization of the final photon in a strong magnetic field has also been found. It has been shown that polarizations of the initial and the final photons are independent except for the case of normal linear polarization of the initial photon., Comment: 6 pages, 2 figures

The process of electron-positron pair production by two photons in a strong magnetic field has been studied. The process kinematics is considered, and the probability amplitude for arbitrary polarizations of particles is found. The resonance conditions are established, and the resonant cross-section is estimated in the case where the electron and the positron occupy the lowest levels ($l_{e} = 1$, $l_{p} = 0$) that satisfy these resonance conditions., Comment: 7 pages, 2 figures

Resonant e+e- pair production by an electron in a magnetic field near the process threshold has been analytically studied. Using the Nikishov's theorem an estimation of the number of events has been made in the magnetic field equivalent to laser wave in the SLAC experiment [D.Burke et.al. Phys. Rev. Lett.79, 1626 (1997)]. The obtained estimation is in reasonable agreement with the experimental data., Comment: 6 pages, 2 figures

The electron-positron pair production by an electron in a strong magnetic field near the process threshold is considered. The process is shown to be more probable if the spin of the initial electron is oriented along the field. In this case, the probability of the process is $\sim10^{13} s^{-1}$ when the magnetic field strength is $H=4\cdot 10^{12}$ G., Comment: 5 pages, 3 figures, 1 table

The photon-induced process of electron-positron pair creation in a strong homogeneous magnetic field, provided that the polarization of particles is arbitrary, has been considered. The polarization of a photon is described in terms of the well-known Stokes parameters, and the relevant probabilities of the process turn out to have simple analytical expressions, which allows us to analyze the polarization and spin effects. A substantial influence of the linear polarization of a photon on the spin orientations of electrons and positrons has been demonstrated., Comment: 8 pages, 4 figures, LaTeX; corrected typos

Spin and polarization effects and correlations between them in the processes of pair production by a photon and synchrotron radiation in a magnetic field are considered. Expressions for the probabilities of the processes with arbitrary polarizations of the particles are obtained. These expressions are analyzed in detail in both the lowest Landau levels and ultrarelativistic approximations., Comment: RevTeX, 12 pages, 8 figures, published in Physical Review D