Contour plots of the analytical potential energy surfaces fitted to ab initio points, corresponding to the reactant channel for R_CH = 1.1199 Å (bottom panel) and to the products channel for R_CS = 1.568 Å (top panel). Energies are in eV. For the products, the energies are shifted by 3.526 eV, so that their point of zero energy corresponds to the CS(r_eq) at an infinite distance from H. The contours correspond to 0 and ± 1 meV in order to show the dependence of the potential at long distances. The units of the color box are eV.