Restoration of coherence effects in high-power excitation of an intramolecular quasicontinuum

Three theoretical models were advanced for the dynamics of molecular multiphoton excitation: (i) The zero-order optically active mode connected by intramolecular random anharmonic couplings to a background manifold. (ii) Molecular eigenstates coupled by random radiative transition dipole moments. (iii) The kinetic master equation approach. It is demonstrated that in the Markoffian limit, as long as the intramolecular vibrational relaxation width is small relative to the Rabi frequency, these three approaches are equivalent. In the case of high-field excitation, coherent quantum effects are exhibited even in a randomly coupled system. Resurrection of the quantum oscillations and coherent pumping can be exhibited in intense field excitation on the time scale of intramolecular vibrational relaxation.