Abstract
We report the velocity-selective magnetic-optical activity of a 87Rb vapor when the counterpropagating pump and probe beams are linearly cross polarized. A semiconductor laser tuned to the D2 line (780 nm) is used to perform the experiment. When a weak axial magnetic field is applied to the vapor, the magnetic-optical activity spectrum reveals a narrow dominant peak, the solitary resonance, corresponding to the cycling transition 5S1/2, F = 2 ↔ 5P3/2, F = 3. The light-shift origin of this spectrum is discussed.