Combining transition state theory with quasiclassical trajectory calculations: application to the nitrogen exchange reaction N+N 2( v)

Abstract

The dynamics of collisions between N atoms and vibrationally excited N 2( v⩽ 15) have been studied using a new method in which quasiclassical trajectories are initiated at suitably chosen transition states. The transition state for a particular vibrational level v is determined by first finding PODSs (periodic orbiting dividing surfaces) on fixed-angle potential energy surfaces for which the action over one cycle of the PODS motion is ( v+ 1 2 ) h. The complete transition state is defined by joining these PODSs together and its phase space is sampled pseudorandomly to select starting points for quasiclassical trajectories. The results of the calculations are compared with those from conventional quasiclassical trajectory calculations on the same LEPS potential energy surface, using the adiabatic reactive sudden version of transition state theory to estimate absolute rate constants from our results. The agreement is good and the combined method brings about a great saving in computing time by eliminating trajectories which do not reach the strong interaction zone.