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,ω) due to scattering from the $2p$ and $2s$ orbitals (i.e., L edges) are observed out to more than 1500.3em0exeV past the binding energy. These results are discussed in context of the recently proposed representation of S(q,ω) 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.