Validity of common assumptions for anomalous scattering
Validity of common assumptions for anomalous scattering is a scholarly work, published in 1984 in ''Physical Review A, General Physics''. The main subjects of the publication include scattering, elastic scattering, radiation protection, angular momentum, Surface weather analysis, physics, quantum electrodynamics, Rayleigh scattering, form factor, quantum mechanics, amplitude, scattering length, X-ray absorption spectroscopy, atomic physics, dispersion relation, and scattering amplitude. The authors use explicit results from a full relativistic numerical calculation of Rayleigh scattering to emphasize that several common assumptions regarding these anomalous scattering factors, still mistakenly used although previously criticized, are not entirely appropriate: (1) The anomalous scattering factors should not be identified with the difference from form factor; (2) the imaginary forward scattering factor ${f}^{\ensuremath{'}\ensuremath{'}}$ is not determined solely from photoeffect at high energy ($\ensuremath{\gtrsim}2m{c}^{2}$); (3) the imaginary forward amplitude includes bound-bound resonance contributions below the photoeffect threshold, which are needed to ensure that the real forward scattering factor obtained from ${f}^{\ensuremath{'}\ensuremath{'}}$ through a dispersion relation goes to a finite value as the threshold is approached from above; (4) the imaginary anomalous amplitudes do not have the angular dependence of the form factor, but rather a weaker angular dependence, with the consequence that the imaginary amplitude can be comparable in magnitude with the real amplitude at some nonforward angles; and (5) the ratio of parallel and perpendicular anomalous amplitudes is not simply $cos\ensuremath{\theta}$.