[en] The relativistic random phase approximation was used to study discrete outer and inner shell transitions of the neon isoelectronic sequence, and to calculate photoionization cross sections of elements of the magnesium and zinc isoelectronic sequences. Model potentials were constructed for the copper and zinc isoelectronic sequences. Molecular processes were investigated and the possibility of an enhanced radiative recombination rate for molecular ions was demonstrated. Detailed calculations of molecular resonance states were completed for H₂ and the experimental data on ion velocity distributions produced in the photoionization of H₂ were interpreted. Charge transfer processes involving multiply-charged ions at thermal energies have been examined and a preliminary selection has been made of those systems for which charge transfer is probably rapid. The mechanisms for the radiative destruction of the lithium excimer were explored; it appears that destruction results preferentially by an accidental predissociation. In order to interpret recent experiments on multiphoton absorption by molecular sodium and the photoionization of Na₂⁺, calculations were carried out of the oscillator strengths of transitions in Na₂. 17 references