Dynamics of highly excited atoms in a broadband-noise electromagnetic field

An analytical classical theory describing the dynamics of a Rydberg atom exposed to broadband-noise electromagnetic radiation is developed. The Fokker-Planck equation governing the diffusion excitation and ionization of the atom is derived. The classical diffusion of the atomic electron over Keplerian orbits is shown to be contributed by the noise radiation components, which are in first-order resonance with the Keplerian motion of the electron. The general properties of the diffusion excitation are studied, and the conditions of the applicability of the theory are delineated.