Quantum energy flow during molecular isomerization

Intramolecular energy flow greatly influences molecular isomerizations, particularly when the energy barrier to reaction is low, as in catalytic and biochemical reactions. We discuss here a simple quantum mechanical theory that describes the extent and rate of vibrational energy flow in molecules, and apply it for the first time to predict rates of isomerization. We consider trans-cis photoisomerization of stilbene, which has been extensively studied experimentally. Vibrational flow in stilbene plays a crucial role in moderating isomerization; the rate both in supersonic jets and low pressure gases is well described by the theory treating quantum flow. (C) 1997 Elsevier Science B.V.