Vibrational states of the triplet electronic state of H3+. The role of non-adiabatic coupling and geometrical phase

TL;DR

This study calculates the vibrational energies of the triplet H3+ ion, incorporating non-adiabatic coupling and geometrical phase effects, revealing their significant influence on energy levels.

Contribution

It introduces a diabatization method that accounts for non-Born-Oppenheimer coupling and geometrical phase in H3+ vibrational calculations, improving accuracy.

Findings

Non-adiabatic coupling and geometrical phase affect vibrational energies.

Energy differences of about a wave number are observed when including these effects.

Comparison shows improved modeling of the triplet H3+ state.

Abstract

Vibrational energies and wave functions of the triplet state of the H3+ ion have been determined. In the calculations, the ground and first excited triplet electronic states are included as well as the non-Born-Oppenheimer coupling between them. A diabatization procedure transforming the two adiabatic ab initio potential energy surfaces of the triplet-H3+ state into a 2x2 matrix is employed. The diabatization takes into account the non-Born-Oppenheimer coupling and the effect of the geometrical phase due to the conical intersection between the two adiabatic potential surfaces. The results are compared to the calculation involving only the lowest adiabatic potential energy surface of the triplet-H3+ ion and neglecting the geometrical phase. The energy difference between results with and without the non-adiabatic coupling and the geometrical phase is about a wave number for the lowest vibrational levels.