However, excitation of the 𝑣 = 1 level of one of these modes in the anion results in a fully FC-allowed transition to the neutral 𝑣 = 1 level, as shown on the right side of Figure , leading to new features in the photoelectron spectrum. Hence, IR pre-excitation of negative ions has the potential to access previously unseen neutral vibrational states and, more generally, expand the range of nuclear configurations probed on the neutral potential energy surface.