Structures and energies of low-lying doublet excited states of N-3 from accurate configuration interaction calculations

The low-lying doublet excited states of the azide radical (N-3) have been studied at a highly multireference ab initio level of theory including basis sets up to augmented quadruple-zeta quality. A full hypersurface scan under C-2v restrictions for five low-lying bent N-3 states ((2)A(2), (2)A(1), B-2(1), and two B-2(2)) revealed a highly complex potential surface manifold with many stationary points, conical intersections and multiple surface crossings, all of which have been characterized at a high level of theory. The behavior of these states is discussed, especially as a function of the NNN angle. At least two new low-lying pathways on the excited surfaces leading from the linear to the cyclic-N-3 region were found, both involving the components of the degenerate excited (2)Pi(u) state of linear N-3.