Ionization of atoms in parallel electric and magnetic fields: The role of classical phase space

Abstract

We analyze the influence of classical phase-space structures on the ionization behavior of Rydberg atoms in parallel electric and magnetic fields. Classically, ionization above the Stark saddle-point energy is suppressed for moderate magnetic fields compared to zero magnetic field. The location of a stable periodic orbit in the surface of section serves as a criterion to understand this trend. For strong magnetic fields the effect is reversed, and ionization is enhanced. This fact is related to the onset of global chaos in the Hamiltonian system. Wt: provide an analytic criterion for the field values at which this crossover takes place. [S1050-2947(98)04011-6].