Velocity dependent pump-probe spectroscopy for a five-level system: An application to Rb D2 transitions

Pump-probe double resonance spectroscopy of Rb D2 transitions are reported for co and counter propagating lasers with tunable frequencies. A perturbative analytical solution of the optical Bloch equations is derived for the five-level atomic system to reproduce the experimental results. The optical pumping effect has been taken into account in the theoretical model. Velocity selective peaks can be observed for all velocity groups of atoms by choosing the appropriate pump frequency. The peaks can be narrowed by varying the lower level hyperfine decay rate.