Abstract

The nature of a simple atomic system can profoundly alter in the presence of an external electric or magnetic field. The study of such systems can provide unique insights into problems such as correlated motion, the behavior of non-separable systems, and quantum structure in regimes of irregular classical motion ("quantum chaos"). We have carried out a study of the spectrum of the lithium atom in magnetic fields in the vicinity of 6 T, at energies close to and above the ionization limit. By using cw lasers we have been able to obtain a resolution of 0.001 cm, low by current standards, but much higher than previously obtained. General quantum solutions to the problem are lacking but numerical solutions have been able to account for the spectrum in regions up to the zero-field ionization limit. Studies of the classical motion reveal an essentially textbook transition from orderly to disorderly motion as the energy increases. Although spectra at a given field appear similar to other spectra whose statistics display the expected behavior, when the spectra are compared at different fields, forming an energy level "map," we observe regularities that can be described by simple quantum numbers. Such behavior is unexpected and suggests that a regime that is believed to be one of total disorder actually encompasses periodic motion.

© 1990 Optical Society of America