Ionization in a quantized electromagnetic field

Using the analytically obtained solution of the Schrodinger equation for an electron in a quantized electromagnetic field, the ionization of an atom has been considered in the framework of a simple one-dimensional model. Expressions for the ionization rate and photoelectron spectrum have been derived and analyzed. We discuss a difference between the results obtained in the model in which the electromagnetic field is described classically and the results obtained in the model of quantized electromagnetic field. In particular, in the latter model the photoelectron spectrum can have a minimum at a certain number of absorbed photons. The minimum is a consequence of destructive interference between the contributions of two parts of the interaction operator.