Relaxation of a three-level atom with non-equidistant spectrum interacting with a thermostat and an external stochastic field is studied. The master equation for the reduced density matrix and its solution in the first order of the perturbation theory are obtained. Using quantum regression theorem, explicit formulas for two-time correlation functions and shapes of radiation lines are derived for all types of three-level atoms and the following stochastic processes: a delta-correlated process and a Kubo-Anderson process. The influence of stochastic perturbations of atom’s energy levels and damping constants of adjacent transitions on width of radiation lines is shown.
The relaxation of a pair of dipole-dipole interacting two-level atoms with parallel dipole moments in a large dissipative system is studied on the basis of the generalized coherent states method. The Fokker-Planck equation and its exact solution are obtained. Explicit formulas for two-time correlation functions are given. The influence of the magnitude of the interaction on the shape of the radiation line is investigated.