We study theoretically and experimentally a new mechanism for the rotation of the polarization ellipse of a single laser beam propagating through an atomic vapor with a frequency tuned near an atomic resonance. The results of a theoretical treatment for the case of a J = 1/2 to J = 1/2 atomic transition show that a rotation of the polarization ellipse of the laser beam will occur as a result of ground-state optical pumping and that the angle of rotation is independent of the laser intensity

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... a broad range of laser intensities. The predictions of this theoretical model are tested experimentally through the use of potassium vapor and are found to agree with the experimental data. One of the simplest nonlinear optical interactions is