The maximum intensity of the WL of the Pu M 3 -and M 5 -edge HR-XANES spectra of the PuO 2 sample was set to the literature value (M 3 = 4563 eV and M 5 = 3775 eV). The sample was measured before and after every other sample to ensure energy calibration. All PuO 2 reference spectra were aligned and the spectra of the samples were shifted by energy accordingly. For the comparison of the Pu M 5 -edge HR-XANES and VB-RIXS, the WL of the PuO 2 HR-XANES spectrum was set to 0 eV and the elastic peak of the VB-RIXS was aligned with it. The spectra were normalized to 1 at the maximum of the WL and of the elastic peak for the Pu M 5 -edge HR-XANES and VB-RIXS spectra, respectively for Figure and Figure . For the Pu M 3 -edge HR-XANES spectra, the last region of the post-edge at 4635 eV was normalized to 1 for better comparability of the spectra.