Effects of quantum coherence of an electromagnetic field involved in multiphoton interaction with atoms

Interaction of coherent and squeezed fields with atoms is investigated. Formulas for the variation of the number of photons in a system of two discrete levels are obtained, and the effects of collapse and revival of population oscillations are considered. The ionization decay of an atomic level under the action of coherent and squeezed fields is studied. It is shown that the decay law substantially differs from the exponential decay law for an isolated level.