  We report experimental observation of velocity-selective resonances in the
Doppler-broadened probe absorption spectra of 85Rb and 87Rb D2 transitions in
the presence of a strong copropagating pump laser locked to a frequency within
the Doppler profile of the transition. The set of three dips having the
separation of allowed hyperfine transitions can be moved along the Doppler
profile by tuning the pump laser frequency indicating a resonance between the
pump laser frequency and the velocity shifted probe laser frequency.
