Investigation of the rotation of the plane of polarization close to a resonance

Results are presented of measurements of the rotation of the plane of polarization close to a resonance in sodium and krypton. These measurements were made using a single-frequency dye laser and a polarization method for recording the absorption in the medium. At the maximum sensitivity of 2×10^–8 rad, it was possible to measure the absorption coefficient in sodium at a concentration of 3×10² atoms/cm³.