RELATIVISTIC ATOMIC FORM-FACTORS AND PHOTON COHERENT SCATTERING CROSS-SECTIONS

Tabulations are presented of relativistic Hartree‐Fock atomic form factors F (x,Z), for values of x (=sin(Ï‘/2)/λ from 0.01 to 109 Å−1, for all elements Z=1 to 100. For Z=1, F (x,Z) is given by the exact expression of Pirenne. For Z=2 to 98, x=0.01 to 2.0 Å−1, the tabulated values are those of Cromer and Waber given in the International Tables for X−Ray Crystallography (Vol. IV, 1974), based in part on the work of Doyle and Turner. For Z=21 to 92, x=2.2 to 6.0 Å−1, the present tables are based on the values of Doyle and Turner and additional values (Z=44,60,68, and 74) as given by Overbo. For Z=3 to 20.x=2.2 to 45 Å−1, Z=21 to 92,x=62 to 45 Å−1 the tables are interpolated from values given for 36 elements by Overbo, extended to x=109 Å−1 using Overbo’s corrections to the Bethe‐Levinger K‐shell expression. The remainder of the table is filled in by interpolation and extrapolation, guided for high x‐values by the Bethe‐Levinger result. Tables of relativistic coherent (Rayleigh) scattering cross sections, obtained by numerical integration of the Thomson formula weighted by F2(x,Z), are presented for all elements Z=1 to 100, for photon energies 100 eV (λ=124 Ã…=12.4 nm) to 100 MeV (λ=0.000 124 Ã…=12.4 fm). Departures from the nonrelativistic coherent scattering cross sections tabulated in J. Phys. Chem. Ref. Data 4, 471 (1975) are less than 1% for Z<20. However for a high‐Z element such as lead, for example, the relativistic coherent scattering cross section is systematically higher by less than 0.4% below 1 keV, by 8% at 100 keV and by 13% above 1 MeV. © 1981, American Association of Physicists in Medicine. All rights reserved.