BEATS IN INTERNAL VIBRATIONAL-ENERGY REDISTRIBUTION IN TRANS-STILBENE- A STUDY OF THE QUANTUM AND CLASSICAL CORRESPONDENCE

Starting from recently observed beating patterns in trans-stilbene we consider the correspondence of classical molecular dynamics and quantu m dynamics for the description of the internal vibrational energy redi stribution in molecules. The beat frequency of two modes in 2:1 resona nce is investigated with respect to quantum effects, sensitivity to an harmonic coupling and indirect coupling via a third oscillator. We fin d a robust correspondence between classical and quantum beat frequenci es but a large sensitivity to the coupling terms in the potential. Ref ined anharmonic coupling appears to be needed to resolve the very low frequency beating patterns observed in trans-stilbene.