fig2

Figure 2. XPS spectra of R-PBM and R-PBMN: (A) Pr 3d; (B) Mn 2p; (C) O 1s; (D) Ni 2p (for R-PBMN only, no Ni signal detected in R-PBM). Schemes illustrate the degeneracy of (E) Mn²⁺; (F) Mn³⁺; (G) Mn⁴⁺ 3d orbitals.