This self-contained text introduces readers tothe field of high-energy atomic physics - a new regime of photon-atominteractions in which the photon energies significantly exceed the atomic ormolecular binding energies, and which opened up with the recent advent of newsynchrotron sources.

From a theoretical point of view, a small-parametercharacteristic of the bound system emerged, making it possible to performanalytic perturbative calculations that can in turn serve as benchmarks formore powerful numerical computations. The first part of the book introduces readersto the foundations of this new regime and its theoretical treatment. Inparticular, the validity of the small-parameter perturbation expansion and ofthe lowest-order approximation is critically reviewed. The following chaptersthen apply these insights to various atomic processes, such as photoionizationas a many-body problem, dominant mechanisms for the production of ions athigher energies, Compton scattering and ionization accompanied by creation ofe-e+ pairs, and the photoionization of endohedral atoms (e.g. fullerene). Lastbut not least, the computationally challenging transitions in the electronshell during certain types of nuclear decays are investigated in detail.

Introduction. What is this bookabout.- Box of tools.- Perturbation theory.- Singularities of the amplitudes andof the wave functions.- The Coulombfield. Nonrelativistic case. - The Coulomb field. Relativistic case.- Photoionizationof atoms.- Ionization and excitation by the photon impact at higher energies.- Ionization andexcitation by the photon impact at higher energies.- Double photoionization andrelated processes.- Photoionization of endohedral atoms.- Annihilation ofpositrons with atomic electrons.- Nuclear transitions and electronic shell.