We present a fully relativistic formulation of the theory of electron-nucleus Bremsstrahlung, within the context of self-field QED, as advanced recently by Barut and his co-workers. The Bremsstrahlung emission cross-section, reported here, is also shown to reduce to the standard correct nonrelativistic limit, in the dipole approximation.

Within the context of the time-reversed S-matrix approach to photoionization, and employing a recently proposed strong-field solution to the Schrödinger equation, analytic expressions for the atomic photoionization rates are obtained here without using the dipole approximation. We show that the absorbed photon momentum shows up as a forward-directed momentum component for the photoelectron. All the expressions reported in this work have the correct limits when the dipole approximation is used.

Within the context of Barut's self-field approach to quantum electrodynamics, we show that the exact relativistic expression for the Einstein A-coefficient of atomic spontaneous emission reduces, in the long wavelength approximation, to a form containing electric- and magnetic-like multipole contributions related to the transition charge and current distributions of the relativistic electron. A number of interesting features of the expressions involved are discussed, and their generalization to interacting composite systems is also pointed out.