Figure 5: The stretching potential curves of the five singlet states (, , , , and state) of CH_{2} as functions of the bond length with the ∠HCH fixed at (a) 180°, (b) 175°, and (c) 160°, respectively; The Renner-Teller terms , , , and () as functions of the bond length with ∠HCH fixed at (d) 180°, (e) 175°, and (f) 160°, respectively. is fixed at 2.09 bohrs, and the zero energy is taken at the CH_{2} () minimum.