Atoms in Strong Fields

This book collects the lectures given at the NATO Advanced Study Institute on "e;Atoms in Strong Fields"e;, which took place on the island of Kos, Greece, during the two weeks of October 9-21,1988. The designation "e;strong field"e; applies here to an external electromagnetic field that is sufficiently strong to cause highly nonlinear alterations in atomic or molecular struc- ture and dynamics. The specific topics treated in this volume fall into two general cater- gories, which are those for which strong field effects can be studied in detail in terrestrial laboratories: the dynamics of excited states in static or quasi-static electric and magnetic fields; and the interaction of atoms and molecules with intense laser radiation. In both areas there exist promising opportunities for research of a fundamental nature. An electric field of even a few volts per centimeter can be very strong on the atom- ic scale, if it acts upon a weakly bound state. The study of Rydberg states with high reso- lution laser spectroscopic techniques has made it possible to follow the transition from weak-field to strong-field behavior in remarkable detail, using static fields of modest lab- oratory strength; in the course of this transition the atomic system evolves from one which can be thoroughly understood in terms of field-free quantum numbers, to one which cannot be meaningfully associated at all with the zero-field states of the atom.