Non-Born-Oppenheimer correction to theH3+potential from experimental data

Abstract

The spectrum of ${\mathrm{D}}_3^{+}$ is analyzed using a spectroscopically determined effective ${\mathrm{H}}_3^{+}$ potential [B. M. Dinelli, S. Miller, and J. Tennyson, J. Molec. Spectrosc. 163, 71 (1994)] and an accurate ab initio potential [G. C. Lie and D. Frye, J. Chem. Phys. 96, 6784 (1992)]. Calculations suggest that the major error in the potential of Lie and Frye is due to the Born-Oppenheimer approximation. ${\mathrm{D}}_3^{+}$ spectroscopic data are used to construct both Born-Oppenheimer and mass-dependent adiabatic surfaces for the ${\mathrm{H}}_3^{+}$ system by fitting only one parameter. These surfaces reproduce the fundamental rovibrational transitions of ${\mathrm{H}}_3^{+}$ and ${\mathrm{D}}_3^{+}$ to within 0.03 ${\mathrm{cm}}^{\mathrm{-}1}$. An accurate adiabatic surface has been determined for a polyatomic molecule.