Determination of polarization relaxation times of atomic levels

Rotation of polarization plane of a probe signal under influence of a time-advanced intense pulse is investigated taking into account optical pumping of atoms in a resonant medium. A formula is derived for the angle of rotation of polarization plane of the probe signal. It follows from this formula that modification of the polarization plane is caused by two processes: radiative decay of atoms and collision-induced redistribution of atoms over magnetic sublevels. It is shown that this method enables direct measuring long times of atomic collisions on the background of short times of the radiation decay.