Changing the chirp property of ultrashort pulses, the spectra of intensity and phase of the pulses after transmitting through ethanol solution of cyanine dye were measured with second-harmonic-generation frequency-resolved optical gating (SHG-FROG) method. Anomalous dispersion due to the absorption of the dye solution was not observed when the pulses were negatively chirped and their intensity were large. This phenomenon is well explained by suppression of the absorption by pump-dump process based on wave packet motion along the shifted harmonic potential model. (C) 2004 Elsevier B.V. All rights reserved.