  The influence of a repump laser on a nearly degenerate four-wave-mixing
(NDFWM) spectrum was investigated. We found the amplitude and line shape of the
NDFWM depended strongly on the detuning of the repump field. A five-peak
structure was observed. And at some certain repump detuning a dip appeared at
the central peak. A rough analysis was proposed to explain this effect.
