A global potential energy surface for H$_3^+$

Abstract

A globally correct potential energy surface (PES) for the H + 3 molecular ion is presented. The Born-Oppenheimer (BO) ab initio grid points of Pavanello et al. [J. Chem. Phys. 136, 184303 (2012)] are refitted as BOPES75K, which reproduces the energies below dissociation with a root mean square deviation of 0.05 cm −1 ; points between dissociation and 75 000 cm −1 are reproduced with the average accuracy of a few wavenumbers. The new PES75K+ potential combines BOPES75K with adiabatic, relativistic and quantum electrodynamics (QED) surfaces to provide the most accurate representation of the H + 3 global potential to date, overcoming the limitations on previous high accuracy H + 3 PESs near and above dissociation. PES75K+ can be used to provide predictions of bound rovibrational energy levels with an accuracy of approaching 0.1 cm −1 . Calculation of rovibrational energy levels within PES75K+ suggests that the non-adiabatic correction remains a limiting factor. The PES is also constructed to give the correct asymptotic limit making it suitable for use in studies of the H + + H 2 prototypical chemical reaction. An improved dissociation energy for H + 3 is derived as D 0 = 35 076 ± 2 cm −1 .