Pump-probe spectroscopy of cold Rb-87 atoms in various polarization configurations - art. no. 043808

We investigate systematically pump-probe spectroscopy of cold Rb-87 atoms p roduced by a magneto-optical trap. The pump-probe spectra are measured with out the presence of the trapping beams or any optical molasses. Various pol arization configurations of the probe and pump fields result in very differ ent spectra of probe absorption. The observed spectra exhibit a dispersive profile, a dispersionlike profile, a Lorentzian profile, or a dispersive pr ofile plus a Lorentzian profile. The widths of all the spectral profiles ar e narrower than the natural linewidth of the excited state. Our work clarif ies the mechanisms behind these different spectral profiles and provides es sential information for the pump-probe spectroscopy of cold atoms.