Magnetooptical Resonances in Cells with Residual Buffer Gas in Elliptical Polarization of Radiation

The dependence of the fluorescence intensity of Cs vapor irradiated by elliptically polarized light resonant with the F = 4 -> F = 5 transition on the scanned magnetic field has a complex shape a narrow dip against the background of a broad peak. It is found experimentally that the dip is due to the small component of the magnetic field orthogonal to the direction of the laser beam. A two-level atom model with degenerate angular-momentum states predicts an order of magnitude lower contrast of this dip. The experimentally observed contrast of the dip can be explained by assuming that due to the low buffer-gas pressure in the optical cell, part of the resonant atoms is able to return to the laser beam without thermalized collisions with the wall of the cell, increasing the contrast. In addition, accounting for all optical transitions of the D-2-line and the optical pumping of the hyperfine-structure components of the ground state is a fundamental point for the interpretation of the experimental results.