(eq 3) 
with λ in, e.g., Ångstroms; the "anomalous" scattering factor f′ (depending on xray energy E and the atomic number Z); and the small nuclear Thomson term f_{NT} [10,11]. f′ can also be expressed in terms of a small relativistic correction term f_{rel}, Z and the function f_{1} often used to characterize these form factors:
(eq 4) 
(eq 5) 
The angular factor f_{0} is identical to the values f(q) or F(x,Z) given in Hubbell et al. [12], Hubbell and Øverbø [13], and Schaupp et al. [14] and use q instead of x, with x = q/4π.
(eq 6) 
The imaginary component Im(f) = f″ is directly related to the atomic photoabsorption crosssection given as τ_{PE} or σ_{PE} in different references:
(eq 7) 
Fundamental constants and conversion factors are given in ref. [15]. Conventionally, the total interaction crosssection σ_{tot} is represented as a sum over the individual photon interaction crosssections:
(eq 8) 
These crosssections would conventionally be given in barns/atom. This would be directly related to the linear attenuation coefficient (µ) in cm^{1}, and the mass attenuation coefficient in cm^{2}/g. The mass attenuation coefficient is conventionally given by the symbol [µ/ρ] = σ/uA, where σ is the crosssection in barns/atom, u is the atomic mass unit, and A is the relative atomic mass of the target element. Coefficients for converting between these units are given by many authors [16]. (See the table header in section 13 and the element header information accessed through the online database.)
This paper develops the approach covered in Chantler [16] and makes extensive reference to this earlier work, which will therefore be denoted in what follows as C95. Table 1 summarizes the type of use to which this tabulation (and that of C95) may be put. It summarizes the typical equation to use (with reference to column headings in the current tabulation) and gives the author's current personal recommendation of a useful or appropriate reference for additional information or coefficients as might be needed.
Form factors for forwarding scattering  section 8.1  Direct use or interpolation, with (eq 4) 
Form factors for significant momentum transfers  section 8.2  (eq 4) and (eq 5) or refs [13,14], [29] or [61] 
Calculation of structure factors  section 8.3  As section 8.2 but also (eq 1) 
Refractive indices  section 8.3  As section 8.2 but also (eq 2) 
Crystallography (diffraction)  section 8.4  As section 8.3 but also see text for references 
Multilayer reflectivity, transmission  section 8.4  As section 8.2 and section 8.3 but also see text for references 
Electron density studies  section 8.5  As section 8.3 but also (eq 11) 
Sum rules  section 8.6  As section 8.2 but also see text for references 
Computation of scattering processes  section 8.7  As section 8.2 but also (eq 12), (eq 14), (eq 1), (eq 16), (eq 17), (eq 18), and (limited) (eq 13) and (eq 15) (see text) 
Photoelectric crosssections, linear absorption coefficient, or mass absorption coefficients  section 8.8  Direct use or interpolation, with conversion as given in table headers as needed 
Xray Attenuation [Medical imaging, transmission studies]  section 8.8  Direct use of total mass attenuation coefficient for Raleigh scattering 
Xray Attenuation studies with alternate scattering estimates  section 8.8  Direct use of mass absorption coefficient, with (eq 19) and possibly refs. [2], [13], [29] 
Xray Attenuation of crystalline samples  section 8.8  Direct use of mass absorption coefficient, with (eq 19) and section 8.7 
Angledependent scattering processes  section 8.8  Not applicable in general  see text 
Highenergy attenuation, above 100 keV  section 8.9  Direct use of mass absorption coefficient, with (eq 19), (eq 8), and possibly refs [2], [12,13], and [29] 
Highenergy (γray) attenuation, above 1 MeV  section 8.9  See refs [12,13] 
VUV studies  section 8.10  Directly, but with caveats and see also ref. [33] 
Kshell studies & fluorescence yields  section 8.11  Directly, but see text 
Electron scattering  section 8.14  (eq 21), and see text 
