Non-Markovian quantum relaxation and theory of spectral lines width

The quantum equation of relaxation with non-Markovian terms in the approximation of short-time memory is derived. The correlation functions for a single two-level atom and system of two dipole-dipole interaction of atoms in the external regular fields and the contour of the radiation lines are calculated. Accounting Non-Markovian effects leads to a more vivid expression of dipole-dipole interaction.