Introduction

Zusammenfassung

The ionization of a quantum system (atoms, molecules, ions) is called nonlinear if the condition ω < E _i is fulfilled, where ω is the photon energy of radiation (or frequency) and E _i is the binding energy of the outermost electron in this system. In this text we will focus only on nonlinear ionization of atomic quantum systems. Such an ionization of an atom, however, contradicts the Einstein relation for the atomic photoeffect, which is given by the inequality of opposite sign, i.e., ω > E _i. However, multiphoton ionization, Kω > E _i (K is an integer) is in agreement with Einstein’s relation.