Pulsed laser saturation spectroscopy: Observation of power broadening by optical nutations

High-resolution saturation spectroscopy of atomic resonance lines with a pulsed tunable dye laser can be performed with a variable time delay between bleaching and probing. Measurements for the Na D₂ line reveal an anomalous time dependent power broadening which cannot be explained within a hole burning model, but is ascribed to a line splitting by optical nutations. The magnitude of the effect is in agreement with recent semiclassical calculations.