Figure shows that L-PDFT and MC-PDFT PESs are in excellent agreement with XMS-CASPT2; correctly reproducing the degenerate 1 ∆ u states as ξ → 0. Figure shows the excited states of all the methods with the zero of energy set to the ground state minimum energy to highlight the difference in vertical excitation energies from the ground state. That figure shows that all the methods produce different vertical excitation energies such that all the PDFT methods except CMS-PDFT have lower excitation energies for 1 Σ - u and 1 ∆ u states than does XMS-CASPT2. The CMS-PDFT method, despite its inability to recover the degenerate 1 ∆ u states, yields vertical gaps in good agreement with XMS-CASPT2 except for the uppermost 1 ∆ u state.