to an infinite separation of all electrons and nuclei. Because the absolute energy of the PES of Ref. [11] is unknown, the origin of this surface is chosen in such a way that the asymptotic energy of the infinite separation between H$_{2}$( r =1.4 a.u.) and H − is the same as in the present study. 2 4 8 16 32 R  (a.u.) -1.7 -1.69 -1.68 -1.67 -1.66 -1.65 -1.64 -1.63 Energy (a.u.) -1.703 -1.702 r =1.4 r =1.6 r =1.2 r =1.8 r =2.0 r =1.0 r =2.2 r =2.4 r R FIG. 3: (Color online) Comparison of the present H − 3 PES (circles) in Jacobi coordinates with the results from Ref. [10] (crosses on the dashed lines) and Ref. [11] (solid blue lines with no symbols) for γ = 0 ° . The PES are shown as a function of R for eight different values of r . The r = 0 . 8 a.u. curve is not shown here because it is located at a higher energy. Symbols indicate the geometries for which the actual ab initio calculations have been performed. The continuous lines connecting the points are obtained by interpolation. No ab initio energies are available for the PES of Ref. [11]: the solid lines without symbols are obtained directly from the analytic formula and the Fortran subroutine provided in Ref. [11]. Notice the logarithmic scale in R variable. The inset enlarges the region of the minimum of the PES close to equilibrium region at r = 1 . 4 a.u. 9