Model for atomic multiphoton ionization via Rydberg states

A model to treat multiphoton ionization through Rydberg states, taking into account blackbody radiation and other processes which lead to ionization with transfer of excitation among the closely-spaced highly excited Rydberg states is presented. The basic idea is to make the rate equations tractable by compacting all of the Rydberg states that experience physically similar processes into a single 'bath' in the equations. The model is applied to sodium Rydberg atoms and the predictions show excellent agreement with experiments. (orig.)