We report the observation of the dissociation of an electronically-excited molecule (Rb-2) with an atomic wavepacket and time-delayed parametric four-wave mixing. The dynamics of the molecular dissociation transient are captured by the temporal histories of the relative number densities of the Rb product states, determined by reference to the amplitude and phase of the Fourier (spectral) components of the wavepacket. Clear experimental evidence of the appearance of atomic fragments (7s, 5d, 6p, 4d, and 5p) generated by dissociation is observed in the pressure-dependent temporal behavior of the amplitude of the 608 cm(-1) (7s-5d) wavepacket spectral component. (C) 2003 Elsevier B.V. All rights reserved.