The unoccupied and occupied Pu 5f and 7p states can be probed by X-ray absorption and X-ray emission spectroscopy, respectively. It is possible to record an X-ray absorption spectrum in different experimental modes. In a transmission mode experiment at the An M 4,5 -edge absorption edge, electrons are excited from the 3d shell to 5f unoccupied states (and diffuse orbitals with 7p character), 3d→5f(7p), following the selection rules ΔL = ±1, ΔJ = 0, ±1 (cf. Figure ). The shape and broadening of the XANES spectrum are influenced by the 3d core-hole in the final state of the excitation process.