High-level ab initio studies of unimolecular dissociation of the ground-state N 3 radical

A comprehensive study of the unimolecular dissociation of the N 3 radical on the ground doublet and excited quartet potential energy surfaces has been carried out with multireference single and double excitation configuration interaction and second-order multireference perturbation methods. Two forms of the N 3 radical have been located in the linear and cyclic region of the lowest doublet potential energy surface with an isomerization barrier of 62.2 kcal/mol above the linear N 3. Three equivalent C 2v minima of cyclic N 3 are connected by low barrier, meaning the molecule is free to undergo pseudorotation. The cyclic N 3 is metastable with respect to ground state products, N( 4S)+N 2, and dissociation must occur via intersystem crossing to a quartet potential energy surface. Minima on the seams of crossing between the doublet and quartet potential surfaces are found to lie substantially higher in energy than the cyclic N 3 minima. This strongly suggests that cyclic N 3 possesses a long collision-free lifetime even if formed with substantial internal excitation. © 2005 American Institute of Physics.

Duke Scholars

Author Peng Zhang Chemistry