Bloch k-selective resonant inelastic scattering of hard x rays at valence electrons of Ni in NiAl

We have measured x-ray fluorescence spectra from a stoichiometric NiAl single crystal after resonant excitation at the Ni K edge using synchrotron radiation. The shape of the spectra strongly depends on both excitation energy and scattering angle. This effect can be understood by considering a resonant inelastic-scattering process leading to a law of Bloch k-momentum conservation. We find clear evidence of this Bloch k-selection rule in the hard x-ray region. The measured spectra an in good agreement with calculated spectra based on a linearized augmented plane wave band-structure calculation.