This volume contains papers associated with the conference "Atomic Spectra and Collisions in External Fields II", that took place July 30-31 1987 at Royal Holloway and Beford New College. The first meeting of this name was held at the National Bureau of Standards in Gaithersburg, Maryland in 1984, and, if any tradition can yet be said to have been established in the series, it is that the proceedings be written after the conference. We hope thereby to preserve some impression of the discussions that took place, which in both cases were vigorous and unihibited. Both meetings happen to have convened in proximity to major developments in the field. At the time of the first conference, results of experimental measurements of dielectronic recombination in electron ion beams were beginning to appear. These showed large discrepancies with theoretical calculations, which were attributed to the effects of rather weak electric fields on the highly-excited states that mediate the recombination process. This conjecture gave rise to widespread concern in the plasma physics community that the representation of dielectronic recombination in existing plasma models, in which it plays an important role in energy and ionization balance, might be seriously in error due to neglect of the effects of electric and magnetic fields. The subject of field effects on recombination processes was thus a major focus of the 1984 meeting.

Inhalt
I. Spectroscopy and Collision Physics of Atoms in D.C. Fields.- A. Magnetic Fields.- Laser Spectroscopy of the Diagmagnetic Hydrogen Atom in the Chaotic Regime.- Strongly Magnetized Atoms - in the Laboratory and in the Cosmos.- Implications of New Evidence on Quasi-Landau Spectra for a Unified Treatment of Collisions and Spectra.- Magnetic Rotation Spectroscopy with Synchrotrons and with Lasers.- Photoabsorption and Photoionization of an Atom in a Magnetic Field.- Atomic Diamagnetism.- Oscillations in Absorption Spectra of Atoms in Magnetic Fields.- Spectra of the Strongly Magnetized Hydrogen Atom Close to the Ionization Threshold.- Accurate Eigenergies for the Magnetized Hydrogen Atom.- Liapunov Exponents for the Diamagnetic Kepler Problem and the Transition from Regular to Irregular Motion.- Cross Section for Potential Scattering in the Presence of a Magnetic Feld and Limit for B?0.- The Hydrogen Atom in a Strong Magnetic Field.- B. Electric Fields.- The Hydrogen Atoms in Strong Electric Fields.- Quantum Beats in the Electric-Field Mixing of the n=2 States of Atomic Hydrogen.- Noble Gas Atoms in Strong DC Electric Fields.- An Atomic Interferometer.- Effect of Polarizability of Alkali Dimers in Electron and Positron Scattering.- C. Combined Electric and Magnetic Fields.- Highly Excited Barium Rydberg Atoms in External Electric, Magnetic, and Combined Fields.- Experimental Investigation and Analysis of Rydberg Atoms in the Presence of Parallel Magnetic and Electric Fields.- Negative Ion Photodetachment in a Static External Field.- Wavefunction Localization for the Hydrogen Atom in Parallel External Electric and Magnetic Fields.- II. Chaos In Atoms in D.C. And Low-Frequency Fields.- Some Aspects of Quantum Chaos.- Quantum Chaos: Destruction and Scars of Symmetries.-Stochastic Formulation of Energy Level Statistics: Application to the Hydrogen Atom in a Magnetic Field.- Highly Excited Hydrogen Atoms in Strong Microwaves.- Chaos in One-Dimensional Hydrogen.- Two-Frequency Microwave Quenching of Highly Excited Hydrogen Atoms.- III. Laser-Atom Interaction at High Intensities.- Atoms in Intense Optical Fields: Pondermotive Forces and Above-Threshold Ionization.- Electron Energy Spectra in High Intensity Multiphoton Ionization.- H2 in Intense Laser Radiation - Multiphoton Two Electron Direct Processes.- Multiphoton Ionization of Atomic Hydrogen by Extra Photons.- Strong-Field Excitation of Continuum Resonances.- Low-Energy Radiative Scattering in a Laser Field.- New Results on Multiphoton Free-Free Transitions.- Multichannel Multiphoton Ionization of the Hydrogen Atom by a Chaotic Field: Role of Polarization.- Participants.