Near-edge elastic photon scattering from dilute aqueous ions

For ions in aqueous solutions, measurements of elastic photon scattering cross-sections have been made in the vicinity of core atomic orbital energies. It is proposed that the aqueous system provides a suitable situation for testing predictions obtained through use of the independent particle approximation (IPA); using intermediate atomic number elements, and at ionic concentrations ranging from 0.01 to 0.1 M/l, resonance structures accord with predictions of elastic scattering cross-sections calculated within IPA. Conversely, at higher ionic concentrations (>0.1 M/l) the resonance structure is distorted. The amplitudes calculated using modified form-factors and anomalous scatter factors computed from a Slater exchange potential, were convolved with a Lorentzian of several eV. This results in cancellation of the increasingly rapid fluctuations, producing a smoothly continuous cross-section across the ionisation threshold.