A semiclassical tunneling model for use in classical trajectory simulations

A semiclassical model for tunneling from one classically allowed region on a potential energy surface to another is described. The principal feature of this model, compared to earlier (more ‘‘rigorous’’) multidimensional semiclassical tunneling theories, is that it can be implemented in a straightforward way within the framework of a standard classical trajectory simulation. Applications to several examples of unimolecular isomerization and unimolecular dissociation show that the model is capable of providing excellent results over a wide range of conditions (i.e., coupling strengths, different symmetries of couplings, etc.)