Nonperturbative theory for the QED corrections to elastic electron-nucleus scattering

A potential for the vertex and self-energy correction is derived from the first-order Born theory. The inclusion of this potential in the Dirac equation, together with the Uehling potential for vacuum polarization, allows for a nonperturbative treatment of these quantum electrodynamical effects within the phase-shift analysis. Investigating the 12C and 208Pb targets, a considerable deviation of the respective cross section change from the Born results is found for the heavier target. It is shown that at low impact energies the dispersion effects play no role. Estimates for the correction to the beam-normal spin asymmetry and its accuracy at 5 MeV (for 208Pb and 197Au) are also provided

The ground state of relativistic ions in the limit of high magnetic fields

We consider the pseudorelativistic no-pair Brown-Ravenhall operator for the description of relativistic one-electron ions in a homogeneous magnetic field B. It is shown for central charge not exceeding Z=87 that their ground state energy decreases according to the square root of B as B tends to infinity, in contrast to the nonrelativistic behaviour.Comment: 15 page

Validity of sum rules for the polarization transfer in electron bremsstrahlung

The polarization correlations, which describe the spin transfer from a high-energy spin-polarized electron to the photon in the elementary process of bremsstrahlung induced by strong potentials, obey a strict sum rule in the case of coplanar emission. The proof is carried out within the relativistic partial-wave approach. Further sum estimates are obtained by means of a variational principle under the sole condition that the transition amplitude is linear in the electron wavefunctions and in the photon field. Numerical sum rule results are given for light and heavy bare target atoms in the energy range 1–10 MeV

Relativistic theory for radiative ionization of light atoms by heavy ions

The capture of a quasifree target electron into the continuum of a heavy, fast projectile ion with simultaneous photon emission, known as radiative ionization (RI), is calculated within the relativistic impulse approximation, applying the partial-wave analysis. Comparison is made with the semirelativistic Sommerfeld-Maue (SM) theory and it is shown that there are considerable differences in the absolute cross sections for heavy projectiles and high collision energies. Absolute photon spectra, measured in the collisions of 96.6 MeV/amu U92+ + H2 and 213 MeV/amu U91+ + H2, are well reproduced by the fully relativistic approach

Validity of sum rules for the polarization transfer in electron bremsstrahlung

The polarization correlations, which describe the spin transfer from a high-energy spin-polarized electron to the photon in the elementary process of bremsstrahlung induced by strong potentials, obey a strict sum rule in the case of coplanar emission. The proof is carried out within the relativistic partial-wave approach. Further sum estimates are obtained by means of a variational principle under the sole condition that the transition amplitude is linear in the electron wavefunctions and in the photon field. Numerical sum rule results are given for light and heavy bare target atoms in the energy range 1–10 MeV

Electron and Positron Scattering from Precious Metal Atoms in the eV to MeV Energy Range

This article reports on the scattering of unpolarized and spin polarized electrons and positrons from 28Ni58,29Cu63,46Pd108, and 78Pt196, covering light to heavy precious metal targets. To cover the wide energy domain of 1 eV ≤Ei≤300 MeV, Dirac partial-wave phase-shift analysis is employed, using a complex optical potential for Ei≤1 MeV and a potential derived from the nuclear charge distribution for Ei>1 MeV. Results are presented for the differential and integral cross-sections, including elastic, momentum transfer, and viscosity cross-sections. In addition, the inelastic, ionization, and total (elastic + inelastic) cross-section results are provided, together with mean free path estimates. Moreover, the polarization correlations S,T, and U, which are sensitive to phase-dependent interference effects, are considered. Scaling laws with respect to collision energy, scattering angle, and nuclear charge number at ultrahigh energies are derived using the equivalence between elastic scattering and tip bremsstrahlung emission. In addition, a systematic analysis of the critical minima in the differential cross-section and the corresponding total polarization points in the Sherman function S is carried out. A comparison with existing experimental data and other theoretical findings is made in order to test the merit of the present approach in explaining details of the measurements

Electron and Positron Scattering from Precious Metal Atoms in the eV to MeV Energy Range

This article reports on the scattering of unpolarized and spin polarized electrons and positrons from 28Ni58,29Cu63,46Pd108, and 78Pt196, covering light to heavy precious metal targets. To cover the wide energy domain of 1 eV ≤Ei≤300 MeV, Dirac partial-wave phase-shift analysis is employed, using a complex optical potential for Ei≤1 MeV and a potential derived from the nuclear charge distribution for Ei>1 MeV. Results are presented for the differential and integral cross-sections, including elastic, momentum transfer, and viscosity cross-sections. In addition, the inelastic, ionization, and total (elastic + inelastic) cross-section results are provided, together with mean free path estimates. Moreover, the polarization correlations S,T, and U, which are sensitive to phase-dependent interference effects, are considered. Scaling laws with respect to collision energy, scattering angle, and nuclear charge number at ultrahigh energies are derived using the equivalence between elastic scattering and tip bremsstrahlung emission. In addition, a systematic analysis of the critical minima in the differential cross-section and the corresponding total polarization points in the Sherman function S is carried out. A comparison with existing experimental data and other theoretical findings is made in order to test the merit of the present approach in explaining details of the measurements

Electron Spectroscopy in Heavy-Ion Storage Rings: Resonant and Non-Resonant Electron Transfer Processes

Whereas our understanding of total cross sections for ionization and capture processes in ion-atom collisions is widely viewed as having arrived at a state of adequate maturity, the same cannot be said at all about the dynamics of collisions, multi-electron processes or the electron continua (in target and projectile) which are at the origin of total cross sections. We depict how these processes can be studied favourably in storage ring environments. We present examplesof resonant and non-resonant electron transfer processes, radiative and non-radiative. This is elucidated via the relation of the electron nucleus bremsstrahlung at the high energy tip of the bremsstrahlung spectrum to the radiative electron capture cusp (RECC) and a new approach to determining molecular orbital binding energies in superheavy quasi-molecules in resonant KK charge transfer