Resonant X-Ray Scattering on theM-Edge Spectra from Triple-kStructure Phase in U0.75Np0.25O2and UO2

We derive an expression for the scattering amplitude of resonant x-rayscattering under the assumption that the Hamiltonian describing theintermediate state preserves spherical symmetry. On the basis of thisexpression, we demonstrate that the energy profile of the RXS spectra expectednear U and Np M_4 edges from the triple-k antiferromagnetic ordering phase inUO_{2} and U_{0.75}Np_{0.25}O_{2} agree well with those from the experiments.We demonstrate that the spectra in the \sigma-\sigma' and \sigma-\pi' channelsexhibit quadrupole and dipole natures, respectively.Comment: 3 pages, 3 figures, to be published in J. Phys. Soc. Jpn. Supp