Classical dynamics of an internal Coriolis-induced isomerization of t r a n s -diimide

The isomerization dynamics of a model of vibrationally excited trans-diimide are reported. Energy transfer into the torsional reaction coordinate does not proceed through the resonance processes described in a companion paper. Rather, a Coriolis coupling of the NH stretches to the torsion dominates the reaction when appropriate relative phase relationships are satisfied. Large amounts of energy can be transferred in this process; thus isomerization is observed in as few as three NH stretching periods. Furthermore, the phase relationships appropriate for isomerization are very restrictive, so that a surprisingly well defined average behavior exists for several vibrational periods both prior to and after the reactive event. We have identified a specific dynamic mechanism responsible for trans/cis isomerization and for trapping the reactive trajectories in the cis-configuration. Despite the complexity of this six degrees of freedom model system, the reactive dynamics can be described in a simple manner.