Pseudoprecession of triatomic systems by electron nuclear dynamics theory

A variety of dynamic effects related to the pseudorotation of triatomic sin gly charged species is explored using the electron nuclear dynamics (END) t heory. The concepts relevant to the motion studied are developed through th e analysis of the simplest molecular species capable of pseudorotation, nam ely H-3(+). It is shown that the wave function for this system leads to anh armonicities in the ground-state potential surface, which make the limiting case of circular pseudorotation unattainable. Initial asymmetries between the vibrational modes of the molecule are demonstrated to induce a rotation al mode that in turn couples the vibrational degrees of freedom by action o f the Coriolis force. Two different dissociation channels open up for the c ase of large initial momenta: H-3(+) --> H+ + H + H and H-3(+) --> H+ + H-2 . The latter mechanism is associated with periodic spin exchange between th e two bonding H atoms, which introduces a purely electronic time scale into the process besides the nuclear one and thus represents a typical nonadiab atic process. The Jahn-Teller system C-3(+) exhibits a range of new motiona l phenomena. In particular, a characteristic frequency shift between the tw o orthogonal vibrational coordinates is observed, resulting from the anisot ropy in the curvature of the C-2v minimum Of C-3(+). It is shown that the J ahn-Teller parameters of the system can in principle be determined from ele ctron nuclear dynamics simulations. (C) 2000 John Wiley & Sons, Inc.