Abstract
The pump-probe spectroscopy of cold 87 Rb atoms produced by a magneto-optical trap was experimentally investigated. The pump-probe spectra were measured in the absence of the trapping beam and any optical molasses. Different spectra of probe absorption were resulted by the various polarization configurations of the probe and pump fields. The results also depicted the propogation of pump and probe beams in the orthogonal directions. The mechanisms behind different spectral profiles were also clarified by pump-probe spectroscopy.