Fundamental problems involving the interactions of photons and electrons with atoms and negative ions either in the free state or in the presence of strong static electric or magnetic fields will be studied theoretically. Physical processes to be studied include multiphoton detachment of negative ions in the presence of strong static electric fields, resonant photoionization of Be, electron impact ionization of H and He, multiphoton processes in H, Ar and F-, and photoionization of H in a strong, uniform magnetic field.