Atoms in strong magnetic fields

Abstract

We review recent results of investigations of hydrogen-like systems at magnetic field strengths where the Lorentz forces are comparable to, or larger than, the Coulomb binding forces. This situation is realized for low-lying states at field strengths typical of magnetic white dwarfs and neutron stars, while for Rydberg states already laboratory field strengths are sufficient. We discuss the wavelength spectrum of the hydrogen atom in magnetic fields of arbitrary strength, and describe in which way the spectroscopy of "stationary lines", which appear in this spectrum, has made possible the detection of the largest magnetic field strength ever found in a white dwarf star to date. For Rydberg states in strong laboratory fields we perform a quantitative comparison between experimental and theoretical spectra, and demonstrate that symptoms of "quantum stochasticity" are recovered in the spectra of magnetized Rydberg atoms. In particular we point out that the breakdown of quasi-separability in the quantal problem is closely related to the disappearance of regular orbits in the classical problem. We conclude that magnetized Rydberg atoms lend themselves as ideal objects in which to study, theoretically and experimentally, manifestations of quantum stochasticity.