X-ray Raman scattering with Bragg diffraction in a La-based superlattice

The non-dispersed soft X-ray emission from a La/B4C periodic multilayer irradiated by monochromatic X-rays has been measured as a function of the incident photon energy in the 125-200 eV range for different scattering angles. We have observed a scattered intensity peak at incident energies which shift towards the low-energy side as the value of the scattering angle increases. These observations are interpreted as Raman scattering by the 5p level of lanthanum assisted by Bragg diffraction from the lattice of the periodic multilayer. A simple model based upon the laws of energy and momentum conservation enables us to account for the variation of the incident energy associated with the Bragg-Raman peak.