Nonlinear Spectroscopy of Cold, Trapped Atoms

We report on our studies of atoms contained in a magneto-optical trap using the nonlinear spectroscopy methods. Absorption and four-wave mixing signals are recorded for the probe frequency near the cooling transition frequency and the two methods are compared. The differences in the signal structure and their sensitivity on external conditions are discussed. It is revealed that central feature of these spectra consists of several contributions of different origin.