Potential curves of the Na–H₂ molecule for the C_∞v (top) and C_2v symmetries (bottom). For the C_2v case, the symmetry labeling corresponds to the convention of the reference plane as that containing the molecule and may be different from that of previous publications. We note that states 1²A₂ and 4²A₁ correlated with the 3d asymptote are superimposed at the scale of the figure.