but written as |Ψ K (R) in Eq. ( ) to remind the reader that the Born-Oppenheimer wavefunctions depend upon the geometry R at which Eq. ( ) is solved. As a simple example, two different CXs for the ethylene molecule are plotted in Fig. . As indicated by the molecular structures, these photochemical funnels are often associated with bond breaking and access very different geometries as compared to those sampled in ground-state dynamics. To access the "twistedpyramidalized" CX in Fig. (a), π → π * excitation from the ground state leads to dissolution of the C=C double bond followed by rotation around the intact σ bond. In the "ethylidene" CX of Fig. (b), a hydrogen atom has transferred from one carbon atom to the other.