Using high energy–electron energy loss spectroscopy, transmission electron microscopy, and synchrotron-radiation-based x-ray absorption spectroscopy, we provide the first experimental evidence that Russell-Saunders ($LS$) coupling fails for the $5f$ states of Pu. These results support the assumption that only the use of $jj$ or intermediate coupling is appropriate for the $5f$ states of Pu. High energy–electron energy loss spectroscopy experiments were performed by use of a transmission electron microscope and are coupled with image and diffraction data; therefore, the measurements are completely phase specific.

• Received 17 January 2003

DOI:https://doi.org/10.1103/PhysRevLett.90.196404