Atoms Iii Molecules i Atome Iii Molekle i

Rather different problems can be lumped together under the general term 'laser control of atoms and molecules'. They include the laser selection of atomic and molecular velocities for the purpose of Doppler-free spectroscopy, laser control of the position and velocity of atoms (i.e. laser trapping and cooling of atoms), and laser control of atomic and molecular processes (ionization, dissociation) with a view of detecting single atoms and molecules and particularly separating isotopes and nuclear isomers.

This introduction to Atomic and Molecular Physics explains how our present model of atoms and molecules has been developed during the last two centuries by many experimental discoveries and from the theoretical side by the introduction of quantum physics to the adequate description of micro-particles. It illustrates the wave model of particles by many examples and shows the limits of classical description. The interaction of electromagnetic radiation with atoms and molecules and its potential for spectroscopy is outlined in more detail and in particular lasers as modern spectroscopic tools are discussed more thoroughly. Many examples and problems with solutions should induce the reader to an intense active cooperation.

This book contains contributions to the 172. WE-Heraeus-Seminar “Atoms and Molecules in Strong External Fields,” which took place April 7–11 1997 at the Phys- zentrum Bad Honnef (Germany). The designation “strong fields” applies to external static magnetic, and/or electric fields that are sufficiently intense to cause alterations in the atomic or molecular str- ture and dynamics. The specific topics treated are the behavior and properties of atoms in strong static fields, the fundamental aspects and electronic structure of molecules in strong magnetic fields, the dynamics and aspects of chaos in highly excited R- berg atoms in external fields, matter in the atmosphere of astrophysical objects (white dwarfs, neutron stars), and quantum nanostructures in strong magnetic fields. It is obvious that the elaboration of the corresponding properties in these regimes causes the greatest difficulties, and is incomplete even today. Present-day technology has made it possible for many research groups to study the behavior of matter in strong external fields, both experimentally and theore- cally, where the phrase “experimentally” includes the astronomical observations. - derstanding these systems requires the development of modern theories and powerful computational techniques. Interdisciplinary collaborations will be helpful and useful in developing more efficient methods to understand these important systems. Hence the idea was to bring together people from different fields like atomic and molecular physics, theoretical chemistry, astrophysics and all those colleagues interested in aspects of few-body systems in external fields.

This introduction to Atomic and Molecular Physics explains how our present model of atoms and molecules has been developed over the last two centuries both by many experimental discoveries and, from the theoretical side, by the introduction of quantum physics to the adequate description of micro-particles.

Relativistic quantum electrodynamics, which describes the electromagneticinteractions of electrons and atomic nuclei, provides the basis for modeling the electronic structure of atoms, molecules and solids and of their interactions with photons and other projectiles. The theory underlying the widely used GRASP relativistic atomic structure program, the DARC electron-atom scattering code and the new BERTHA relativistic molecular structure program is presented in depth, together with computational aspects relevant to practical calculations. Along with an understanding of the physics and mathematics, the reader will gain some idea of how to use these programs to predict energy levels, ionization energies, electron affinities, transition probabilities, hyperfine effects and other properties of atoms and molecules.

The development of modern pulsed lasers with power densities larger than 16 ?2 10 Wcm and with very short pulse duration in the femtosecond regime enables experimentalists to study elementary processes such as chemical - actions and excitation mechanisms in di?erent areas in physics in the time domain.