A classical path approach to reactive scattering. I. Use of hyperspherical coordinates

A classical path method is described for treating reactive collisions in three-body systems. The key feature of the method is the use of hyperspherical coordinates, which allow the definition of classical and quantum subsystems in such a way as to be independent of the arrangement of the particles. The "relative" motion and overall rotation are treated classically, while the "arrangement" and internal motion are treated quantum mechanically. The method is applied to the collinear D + HH system on the PK2 potential energy surface. These calculations show a great improvement over quasiclassical trajectory results in the vicinity of the apparent threshold of the reaction.