Semiclassical Calculations of Tunneling Splitting in Tropolone

Abstract

Energy level splittings in tropolone are calculated by using a semiclassical approach for tunneling in multidimensional systems. A potential-energy surface that includes all 39 vibrational degrees of freedom was constructed for the ground electronic state on the basis of ab initio results. Since the method incorporates tunneling within standard trajectory simulations, the full-dimensional dynamics were explicitly treated to provide a clear picture of the dynamical behavior of the system and its effect on tunneling. Level splittings for the ground states of the normal and deuterated species were calculated. We also studied the sensitivity of the splittings to the choice of tunneling path. Mode-selective excitations were used to study the effect of vibrational excitation on the tunneling. It is found that some modes promote tunneling, some suppress it, and some do not affect it. This demonstrates the multidimensional nature of the tunneling process and the importance of properly treating heavy-atom motions.