In the case of the NiO2 ground state band, assignments of features are facilitated by our SFX2C-1e-CCSD(T)/aug-cc-pVTZ calculations, which allow for FC simulations to be performed for detachment transitions terminating in the , in which spectra collected at three photon energies highlight the differing behavior of these features as photodetachment threshold is approached. As discussed in Section IV.C, our assignments for the B peaks all involve odd changes of vibrational quanta in the non-totally symmetric ν2 bending mode and are hence Franck-Condon forbidden.