Spin-Orbit Coupling versus Exchange Interaction in Actinide Metals

摘要

The electronic structure of the actinide metals, Th, U, Np, Pu, Am, and Cm, is investigated using electron energy-loss spectroscopy (EELS) in a transmission electron microscope, together with many-electron spectral calculations. At the N_(4,5) edge, sum rule analysis gives the angular part of the spin-orbit interaction per hole, showing that while light metals (Th and U) follow LS coupling, heavier metals (Pu, Am, and Cm) follow intermediate coupling of the 5f states. The intermediate coupling is near the jj limit for Pu and Am, but strongly shifted towards the LS coupling limit for Cm. At the O_(4,5) edge many-electron spectral calculations show that the prepeak corresponds to a 'forbidden' transition.