It is proposed to study the evolution of excited atomic states in dense media, under the influence of multiple scattering and dynamical screening effects, within the framework of classical and quantum stochastic dynamics. Present applications and comparisons with experiment focus primarily on atom or ion penetration through solids. The fundamental goal is to analyze noise induced dynamics of simple atomic systems in terms of transport theory. Evolution of atomic states strongly perturbed in dense media will be related to the theory of stochastic processes in non-linear dynamic media. Both classical and quantum calculations will be performed, in order to study the interplay of extrinsic stochasticity due to random forces (noise) and intrinsic stochasticity due to (classically) chaotic dynamics. //
