Background proportional enhancement of the extended fine structure in nonresonant inelastic x-ray scattering

We report new measurements and calculations of the nonresonant inelastic x-ray scattering (NRIXS) from Mg and Al for a wide range of momentum transfers, q. Extended oscillations in the dynamic structure factor S (q,omega) due to scattering from the 2p and 2s orbitals (i.e., L edges) are observed out to more than 150 eV past the binding energy. These results are discussed in context of the recently proposed representation of S (q,omega) for core shells as an atomic background modulated by interference between different photoelectron scattering paths, in analogy to the standard treatment of extended x-ray absorption fine structure. In agreement with this representation, we find a strong increase in the atomic background with increasing q with a concomitant enhancement in the amplitude of the extended fine structure. This effect should be generic and hence may enable improved measurement of the extended fine structure in a wide range of materials containing low-Z elements.