were carried out using Q-Chem. We computed FCFs with the LEVEL16 program, which solves the quantum vibrational problem numerically using potential energy curves provided by the user. In these calculations, the interatomic potential is represented by analytic functions: exponential functions (fit to the provided potential energy curves) represent asymptotes and the regions in between the sampled points are interpolated with cubic splines. The complete potential energy curves for both non-relativistic and spin-orbit corrected states are given in the Supplementary Information (SI). the 1 2 ∆, 1 2 Π, and 2 2 Σ correspond to a singly occupied d-type orbital. Although atomic states originating from a singly occupied d-type orbital have the same electronic angular momentum, the diatomic states vary with respect to its projection on the molecular axis, giving rise to three types of molecular states. Table and Fig. show non-relativistic EOM-EA-CCSD excitation energies computed at the ground-state equilibrium geometries for ScF + , ScCl + , ScBr + , YF + , YCl + , and YBr + .