An ab initio, analytically fitted, global potential energy surface for the ground electronic state of He3+

Abstract

An analytical, global potential energy surface for the ground electronic potential energy surface (PES) for the He3+ ion has been constructed by fitting ab initio energy values calculated at the QCISD(T)/aug-cc-pVTZ level of theory for 935 geometric configurations to a many body expansion type functional form appended with ion-induced dipole terms to describe the long range interactions. The PES is adiabatically constrained to the ground electronic state by requiring the two atoms with the shortest separation in any particular geometry to be described by the embedded two-body He2+ potential. A transition state for the positional interchange of the middle and end atoms of the linear, centrosymmetric equilibrium geometry is identified and lies about 300 cm−1 below the energy of the He2++He dissociation products. The nature of the PES near a seam of conical intersections between the ground and first excited electronic states occurring at D3h geometries is discussed.