Freezing molecular vibrational energy flow with coherent control

In a previous report, we examined the possibility of 'freezing' intramolecular vibrational energy redistribution (IVR) in organic molecules by using optimal coherent control. Here we describe the new methodology developed to achieve stabilization of initially excited nonstationary states. Our approach combines an approximate but full-dimensional molecular vibrational Hamiltonian, a frequency-domain wavelet representation of the electric field, a fast symplectic propagator to compute the IVR decay, and simulated annealing optimization of the electric field parameters. We find that the complexity of the vibrational wavepacket increases sufficiently slowly with time, so that with available pulse shapers, vibrational dephasing can be 'frozen' for 1-2 orders of magnitude in time beyond the usual IVR decay time. Slowing the IVR clock into the multi-picosecond regime may allow the natural selective reactivity (via Franck-Condon factors) of the initially excited nonstationary vibrational states to emerge. (C) 2002 Elsevier Science B.V. All rights reserved.