Dissipative dynamics in many-atom systems: A density matrix treatment

The dynamics of a many-atom system are described in terms of the density operator solution of the Liouville-von Neumann equation, for either isolated or dissipative (open) conditions. The treatment introduces a partial Wigner transform of the density operator of the isolated system or of a primary region of interest, respectively, classifying degrees of freedom as quantal or quasi-classical. A secondary region (the medium) is treated as a stochastic environment leading to a dissipative dynamics of the primary region. Dissipative phenomena are described in terms of dissipative potentials and rate operators. The quantum and quasi-classical degrees of freedom can be identified with the electronic and nuclear variables of a many-atom system to provide a description of electronic rearrangement and excitations during dissipative phenomena. (C) 2002 Wiley Periodicals, Inc.