Toward polyatomic wave packet decomposition: Final state effects

We present numerical studies of femtosecond time-resolved probes of coupled wave packet dynamics in model polyatomic systems. Of specific interest is the possibility of using the structure and symmetry of the final states acc essed by the probe field to discern vibrational energy flow. Simple wave pa ckets can often exhibit classical localization, thus facilitating a mechani stic, trajectory-like picture of the quantum dynamics. This feature, howeve r, does not necessarily survive in complex multidimensional problems due to differing quantum mechanical dephasing rates in different degrees of freed om. To recover a classical-like picture of energy flow between coupled vibr ational modes, we introduce a final-state-resolved measure of wave packet d ynamics, a low-frequency band-pass filter of the signal, which is specifica lly sensitive to intermode energy flow.