Measurements of Rayleigh scattering and relativistic calculations of incoherent scattering functions |
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Authors: | Sylvian Kahane |
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Institution: | Physics Department, Nuclear Research Center, Negev, P.O. Box 9001, Beer-Sheva 84190, Israel |
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Abstract: | Recent measurements of Rayleigh scattering employing neutron capture γ-rays are presented. Experimental conditions are achieved such that the Rayleigh contribution is dominant and much larger than the other competing coherent processes. A detailed comparison with the modified relativistic form factor (MRFF) approximation is made and it is concluded that the latter overestimates the cross-section by 3–4%. New calculations of S, the incoherent scattering function, are presented in the relativistic treatment of Ribberfors and Berggren, using multiconfiguration Dirac–Fock relativistic wavefunctions. Tables of S, for Z=1–110, are shown on a momentum transfer mesh identical to previous non-relativistic calculations. S has been calculated at a representative angle θ=60° and energies compatible with the presentation mesh. For other scattering angles, the values presented in the tables are accurate to within 1–2% for momentum transfers larger than 0.1 Å?1. In the region below 0.1 Å?1 the accuracy worsens with decreasing momentum transfer, reaching 6% at 0.01 Å?1 and 10% at 0.005 Å?1. The same multiconfiguration wave functions were used to evaluate new MRFFs. The new elastic scattering cross sections differ by 3–6% compared with calculations based on single configuration wave functions. |
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Keywords: | Photon elastic scattering Rayleigh scattering Compton scattering Incoherent scattering function Form factors |
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