The Pu M 3 -and M 5 -edge HR-XANES and Pu M 5edge VB-RIXS were recorded at the ACT station of the CAT-ACT beamline at the Karlsruhe Light Source (KIT, Germany). 118 At this 2.5 T superconducting wiggler beamline, the beam was vertically collimated by a Si mirror then monochromatized by a Si(111) double crystal monochromator and focused by a toroidal double-focusing Si mirror. A slit was used to confine the beam at the sample position to a spot size of 500/200(Pu 3+ (aq)) × 500 μm for the Pu M 5 -edge HR-XANES and VB-RIXS experiments. The beam size for the Pu M 3 -edge HR-XANES experiments was approximately 1 × 1 mm.