Pseudoprecession of triatomic systems by electron nuclear dynamics theory

A variety of dynamic effects related to the pseudorotation of triatomic singly charged species is explored using the electron nuclear dynamics (END) theory. The concepts relevant to the motion studied are developed through the analysis of the simplest molecular species capable of pseudorotation, namely H \documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{+}$\end{document} . It is shown that the wave function for this system leads to anharmonicities 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 rotational mode that in turn couples the vibrational degrees of freedom by action of the Coriolis force. Two different dissociation channels open up for the case of large initial momenta: \documentclass{article}\pagestyle{empty}\begin{document}$\mathrm{H_{3}^{+}\to H^{+}+H+H}$\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$\mathrm{H_{3}^{+}\to H^{+}+H_{2}}$\end{document} . The latter mechanism is associated with periodic spin exchange between the two bonding H atoms, which introduces a purely electronic time scale into the process besides the nuclear one and thus represents a typical nonadiabatic process. The Jahn–Teller system C \documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{+}$\end{document} exhibits a range of new motional phenomena. In particular, a characteristic frequency shift between the two orthogonal vibrational coordinates is observed, resulting from the anisotropy in the curvature of the C 2 v minimum of C \documentclass{article}\pagestyle{empty}\begin{document}$_{3}^{+}$\end{document} . It is shown that the Jahn–Teller parameters of the system can in principle be determined from electron nuclear dynamics simulations. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 966–988, 2000